fix(cctv): key-gate Ottawa, opt-in Québec video, keep shared slots

Review fixes for #1506.

- Ottawa: use the documented camera list and the city's Traffic Camera
  Images API. The pack is skipped with no request unless
  OTTAWA_CAMERA_CERTIFICATE is set; the certificate is added only at
  fetch time inside the pinned /opendata/ path, and each camera is
  fetched at most once a minute through the shared frame cache.
- Québec 511 video is opt-in (CCTV_QUEBEC_VIDEO_ENABLED=1) and loads
  only after the viewer presses Play; selection, auto-hop, scenes and
  voice no longer contact Québec 511. Credit splits locations (MTQ,
  CC BY 4.0) from video (Québec 511). Interrupted play() is no longer
  reported as an unavailable source; the per-frame listener runs only
  while a Québec camera is selected and the canvas rect is cached.
- Catalog cap: reserved Québec and World slots come only from capacity
  above the 4,000 shared slots, so a lower CCTV_MAX_SOURCES thins every
  pack instead of starving the existing ones. dev-fresh and
  .env.example default to 7,516.
- Throttled frames (World, Ottawa): inside the refresh floor with no
  cached frame the proxy serves the placeholder, never Street View; a
  failed fetch backs off for a minute; the cache is bounded by bytes.
- MJPEG first-frame extraction runs only for sources registered as
  MJPEG (Taiwan Highway Bureau), caps a frame at 2 MB, reads in linear
  time, accepts a CRLF preamble and a boundary that already starts with
  "--", and ends a part without Content-Length at the next delimiter.
  THB hosts are registered in the redirect pin list.
- Tests: World loader policy, Québec loader and opt-in, proxy cooldown
  without Street View, Ottawa signing, cap reservations at 7,516, 4,000
  and 48, overlay Play gate, refresh, visibility and teardown. Guard
  tests check the 4,000 shared slots again.
- Remove the unused standalone Québec preview module and public page.
- Docs: DATA_SOURCES, SECURITY, CURRENT-STATE, CCTV_INTEGRATION, README,
  .env.example, changelog fragment renamed to its full scope.

DATA_SOURCES.md

@@ -116,7 +116,7 @@ The optional Local ADS-B layer and the broadcast-FM receiver use radio you recei
 
 - **Via Lietuva / Eismoinfo (Lithuania).** Public road-camera catalogs and periodically updated still images from [Eismoinfo](https://eismoinfo.lt/), credited to Via Lietuva / eismoinfo.lt in the app. **Off by default.** The camera endpoints are the eismoinfo.lt website backend and are not among the services listed in Via Lietuva's [open-data statement](https://eismoinfo.lt/eismoinfo-backend/content?id=44), whose conditions are attribution and reuse on the same terms. Until the statement is confirmed to cover the camera photos, the pack loads only when an operator sets `CCTV_LITHUANIA_ENABLED=1`; with the flag unset, empty or any other value, the server makes no request to Eismoinfo. `eismoinfo-backend/camera-info-table` is joined by ID to `layer-static-features/VKR`. Without `lks=true`, the latter returns WGS84 `[latitude, longitude]`; the table's `x/y` instead use LKS-94 metres. Only the official HTTPS `/eismoinfo-backend/image-provider/camera/last?id=…` image endpoint is registered. Catalogs use the shared 15-minute cache; frames are fetched on demand and never bundled or archived. These are periodic snapshots, not continuous video. Camera headings are low-confidence estimates. No API key is required. `CCTV_LITHUANIA_MAX_SOURCES` defaults to 400.
 - **Freeway Bureau and Highway Bureau, MOTC (Taiwan).** National freeway cameras use the Freeway Bureau’s keyless [MOTC 2.0 CCTV table](https://tisvcloud.freeway.gov.tw/history/motc20/CCTV.xml), refreshed daily and fetched at runtime (never bundled). Freeway Bureau data follows the [Open Government Data License, Taiwan v1.0](https://data.gov.tw/license); the app credits the Bureau, names the dataset and links the licence. If that catalog is unreachable and no last-good source list exists, the app falls back to the Highway Bureau’s free [provincial-road CCTV XML feed](https://thbapp.thb.gov.tw/opendata/), with attribution as requested by the Bureau. Its MJPEG streams are accepted only from cctv-ss01 through cctv-ss08.thb.gov.tw over HTTPS; the frame proxy extracts one bounded JPEG per request. This fallback covers provincial roads, not national freeways. Neither feed requires an API key. CCTV_TAIWAN_ENABLED=0 disables both; CCTV_TAIWAN_MAX_SOURCES defaults to 600 (bounded to 1–2000).
-- **Québec CCTV (MTQ / Québec 511, Montréal and scenic links).** `public/quebec-cameras.json` contains 680 MTQ positions from the official georeferenced WFS (CC BY 4.0), 426 Montréal camera locations derived from OSM (ODbL 1.0), and 14 scenic records with per-row provenance and accuracy. The 680 MTQ cameras play the operator's five-second MP4 clip directly in the browser from `www.quebec511.info/Carte/Fenetres/camera.ashx?id=<id>&format=mp4`; Québec 511 refreshes those clips every few minutes. A second browser request supplies an approximate map still. The app does not proxy, store, or read video pixels, and no camera images are bundled. Montréal and scenic entries have provider-page links rather than direct frame URLs; their source-page terms apply. The video remains hosted by Québec 511 under its service terms. No API key is required; `CCTV_QUEBEC_ENABLED=0` disables the pack.
+- **Québec CCTV (MTQ / Québec 511, Montréal and scenic links).** `public/quebec-cameras.json` contains 680 MTQ positions from the official georeferenced WFS (CC BY 4.0), 426 Montréal camera locations derived from OSM (ODbL 1.0), and 14 scenic records with per-row provenance and accuracy. The MTQ video is **opt-in** (`CCTV_QUEBEC_VIDEO_ENABLED=1`): the CC BY 4.0 licence covers the camera locations only, and Québec 511's terms for embedding its clips on another site are unconfirmed, so by default MTQ cameras link to the Québec 511 viewer page instead. With the flag set, the 680 MTQ cameras play the operator's five-second MP4 clip directly in the viewer's browser from `www.quebec511.info/Carte/Fenetres/camera.ashx?id=<id>&format=mp4`, only after the viewer presses Play, so Québec 511 sees the viewer's IP address; Québec 511 refreshes those clips every few minutes. A second browser request supplies an approximate map still. The app does not proxy, store, or read video pixels, and no camera images are bundled. The selected-camera credit names both sources: locations MTQ under CC BY 4.0, video Québec 511. Montréal and scenic entries have provider-page links rather than direct frame URLs; their source-page terms apply. The video remains hosted by Québec 511 under its service terms. No API key is required; `CCTV_QUEBEC_ENABLED=0` disables the pack. Confirm Québec 511's terms of use before setting `CCTV_QUEBEC_VIDEO_ENABLED=1` on a public deployment.
 
 - **Google Maps Platform.** You supply your own API key and are bound by [Google's ToS](https://cloud.google.com/maps-platform/terms). Google Maps Content (tiles, geocodes, places) **may not be cached, stored, rehosted, or committed** — this app only ever uses it live, which is the compliant pattern. The "Google" attribution is displayed on the globe and must stay visible. Restrict your key (see [SECURITY.md](SECURITY.md)).
 - **OpenSky Network.** Its license is **non-commercial**, and operational use of the REST API in a live product can require a prior written agreement with OpenSky — even for non-profit/government use. If you deploy this commercially, contact OpenSky for your own terms. The flights layer is a toggle and runs anonymously by default.
@@ -163,7 +163,7 @@ The optional Local ADS-B layer and the broadcast-FM receiver use radio you recei
 - **DelDOT live video cameras.** The keyless `tmc.deldot.gov/json/videocamera.json` catalog supplies active cameras and official `https://video.deldot.gov/live/…/playlist.m3u8` links. The local server transiently buffers bounded MPEG-TS segments in memory and deletes them on session release or idle expiry. No recordings are retained. `CCTV_DELDOT_ENABLED=0` disables the pack. Public availability is not a blanket redistribution license; deployment beyond personal local viewing needs confirmation of applicable DelDOT terms.
 - **Fintraffic weathercams.** The camera list is one keyless GeoJSON request to `tie.digitraffic.fi/api/weathercam/v1/stations` (809 stations / 2,275 presets), sent with the `Digitraffic-User: gods-eye-view` header the service asks clients to identify themselves with and with gzip; frames are stills on `weathercam.digitraffic.fi`, refreshed on each station's 600 s collection interval, which is also the client's ambient-still refresh cadence for this pack (the active camera keeps the usual 10-second refresh). One preset (a fixed camera view) is one camera; stations not `GATHERING` and presets not `inCollection` are dropped. Attribution is required by the CC BY 4.0 licence and is registered in the Data attribution popover. `CCTV_FINTRAFFIC_ENABLED=0` is the kill switch.
 - **DriveBC highway cameras.** The camera list comes from the keyless `https://www.drivebc.ca/api/webcams/` endpoint served by the DriveBC.ca site ([bcgov/DriveBC.ca](https://github.com/bcgov/DriveBC.ca)); frames come from `https://www.drivebc.ca/images/<id>.jpg`, built from the numeric camera id. DataBC's [DriveBC HighwayCams](https://catalogue.data.gov.bc.ca/dataset/bc-highwaycams) catalogue entry publishes the same cameras under the Open Government Licence – British Columbia, but its CSV still lists the retired `images.drivebc.ca` frame URLs, which now return a placeholder. The licence's attribution statement is required and is registered in the Data attribution popover. By default the 250 cameras nearest Vancouver and Victoria load; `CCTV_DRIVEBC_MAX_SOURCES` changes the cap and `CCTV_DRIVEBC_ENABLED=0` turns the pack off. Some cameras in the feed are supplied by partners (TransLink, the City of Vancouver, the City of Surrey, Parks Canada / Alberta Motor Association and others); the feed's per-camera credit is carried onto the camera record and shown beside the provider in the CCTV panel.
-- **City of Ottawa traffic cameras.** The keyless `traffic.ottawa.ca/map/camera_list` JSON supplies an id, coordinates, an English/French description and a type; frames are city-served JPEG stills built from the id at `traffic.ottawa.ca/map/camera?id=<id>`, and only that directory is pinned. MTO cameras carried on the city feed keep their owner as a per-camera credit. The feed publishes no bearing, so headings use the shared id-hash fallback at low confidence, and no status field, so a camera the city takes offline still registers. Frames are fetched at request time and never stored. The city publishes no explicit reuse licence for this feed; deployment beyond personal local viewing needs confirmation of applicable terms. `CCTV_OTTAWA_MAX_SOURCES` caps the pack (default 250, nearest downtown) and `CCTV_OTTAWA_ENABLED=0` turns it off.
+- **City of Ottawa traffic cameras.** Camera images come from the city's [Traffic Camera Images API](https://traffic.ottawa.ca/en/traffic-map-data-lists-and-resources/about-the-data), which requires an access certificate requested through the city's registration form and allows one certificate and user id to fetch a camera at most once every 60 seconds. Set `OTTAWA_CAMERA_CERTIFICATE`; without it the pack is skipped and makes no request. The camera list is the documented keyless `traffic.ottawa.ca/map/service/camera` JSON (camera number, English and French names, coordinates, owner). Frames are `traffic.ottawa.ca/opendata/camera?c=<number>`; the server adds the certificate and the user id `gev` at fetch time, so no catalog response carries the key, and serves each camera from one shared in-memory frame per minute. MTO cameras carried on the city feed keep their owner as a per-camera credit. The feed publishes no bearing, so headings use the shared id-hash fallback at low confidence, and no status field, so a camera the city takes offline still registers. Frames are never stored on disk. The city states no redistribution licence for the images; the certificate request asks how they will be used, so describe the deployment there. `CCTV_OTTAWA_MAX_SOURCES` caps the pack (default 250, nearest downtown) and `CCTV_OTTAWA_ENABLED=0` turns it off.
 - **World cams image subset.** The normal CCTV catalog adds 166 Icelandic Road and Coastal Administration cameras, 1,176 Oregon TripCheck stills, and 1,054 MLIT river cameras from the curated `config/cctv_sources.world-image-cameras.json` export; disable it with `CCTV_WORLD_CAMERAS_ENABLED=0`. The server validates and pins each image URL to its provider path. [Vegagerðin's data-service licence](https://www.vegagerdin.is/vegagerdin/gagnasafn/vefthjonustur/terms-and-conditions) permits reuse with attribution but excludes third-party rights; [ODOT allows TripCheck image use and requests credit](https://www.tripcheck.com/Pages/Frequently-Asked-Questions); MLIT's [site terms](https://www.river.go.jp/kawabou/kwb_apend/html/caution.html) are CC BY-compatible with attribution and warn against high-volume/periodic collection, so those frames refresh at ten minutes per camera. Images are not bundled or persisted; a bounded 32 MB in-memory cache reuses them until the per-source cadence. The 249 NZTA Journey Planner rows are excluded because its [website terms prohibit scraping](https://www.journeys.nzta.govt.nz/about-this-site/terms-of-use); use an authorized API feed or obtain permission before adding those rows.
 - **TxDOT ITS cameras.** The catalog comes from the keyless `its.txdot.gov/its/DistrictIts/GetCctvStatusListByDistrict` endpoint, one call per district. Frames come from the per-camera `GetCctvSnapshotByIcdId` endpoint, which answers JSON carrying a base64 JPEG rather than an image body; the proxy decodes it only for responses from the official TxDOT origin and validates the JPEG header before serving. Only cameras reporting `Device Online` are registered. Districts default to Austin and San Antonio (`CCTV_TXDOT_DISTRICTS`; 25 codes exist statewide); `CCTV_TXDOT_MAX_SOURCES` caps the pack and `CCTV_TXDOT_ENABLED=0` turns it off. Frames are fetched live at request time and are never stored or redistributed.
 - **Tallinn ristmikud.** Intersection camera stills are fetched live from `ristmikud.tallinn.ee` (`/last/camNNN.jpg`). The curated catalog (`config/cctv_sources.tallinn.json`) supplies coordinates and heading priors; only server-registered ristmikud HTTPS URLs are proxied. Frames are fetched at request time and never stored or redistributed. Disable with `CCTV_TALLINN_ENABLED=0`.