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.

SECURITY.md

@@ -71,10 +71,11 @@ The data proxies under `server/providers/` are written so the browser cannot tur
 - **No arbitrary-URL fetching.** The CCTV frame proxy fetches only server-registered camera/frame URLs — clients cannot pass an upstream URL to fetch (SSRF mitigation). Other proxies target fixed upstream hosts.
 - **Live HLS is bounded and origin-pinned.** Registered HTTP(S) HLS sources use a Node puller that rejects redirects and off-origin playlist references, bounds playlists and segment bodies while streaming, and aborts timed-out or released sessions. At most two sessions retain 12 segments/24 MiB each, plus bounded download buffers. Stores are memory-only and idle sessions expire after 15 seconds. RTMP/ffmpeg execution is not enabled. Locally configured source URLs remain an operator trust boundary.
 - **Radio is not an audio relay.** `/api/radio/stations` contacts only allowlisted Radio Browser HTTPS hosts and paths, rejects redirects, rejects any hostname with a loopback/private/link-local/metadata/non-public A or AAAA result, and pins each TLS connection to a validated address. It returns normalized public HTTPS stream URLs; `/api/radio/click/:uuid` applies the same destination policy and accepts only station IDs from the current bounded catalog. The browser then connects directly to the broadcaster after an explicit playback action, so the broadcaster sees the listener's IP address. GEV never proxies, caches, records, or redistributes audio.
+- **Québec 511 video plays in the browser, opt-in and after Play.** With `CCTV_QUEBEC_VIDEO_ENABLED=1`, `/api/cctv/sources` lists, for each MTQ camera, one URL built server-side from its numeric id on `https://www.quebec511.info/Carte/Fenetres/camera.ashx`; the overlay accepts no other host, path or format. The browser loads that clip only after the viewer presses Play for the selected camera, so Québec 511 sees the viewer's IP address, and the panel says so before Play. Selecting a camera by click, auto-hop, a scene or voice never loads it, and switching cameras stops playback. GEV never proxies, caches or reads the video's pixels. With the flag unset (the default) the browser makes no request to Québec 511.
 - **No verbatim client headers upstream.** The CCTV media route is the one route that relays a request header (`Range`, for video seeking). It is parsed and canonicalized before it is forwarded: one `bytes=` range only, with every accepted form — explicit span, open-ended and suffix — bounded to the same 64 MiB ceiling the relay applies to a declared response body. Multi-range, malformed, inverted and non-`bytes` values are dropped and the request proceeds without a `Range`, as RFC 7233 §3.1 prescribes. Bounding the request bounds what is asked for: a response that declares no length — live streamed media, or a chunked body from an upstream that ignores the `Range` — has no ceiling. An upstream request the browser has stopped waiting for is cancelled rather than left running, whether the viewer leaves before the headers arrive or during the body.
 - **Transit fetches registered feeds only.** `/api/transit/vehicles/<id>` resolves the id against `src/data/transitFeeds.js`; the browser never supplies a URL, and a feed that is registered but disabled does not resolve at all. Redirects are followed manually and each hop is validated against the feed's own https origin before it is requested, so an off-origin or downgraded hop is refused rather than contacted. Bodies are capped at 8 MB, the protobuf is decoded server-side under entity-count and string-length ceilings, a differential feed is refused, and snapshots live 15 s in memory with no disk cache. A per-feed admission limiter and a failure cooldown ladder bound what this process can ask of any operator.
 - **Local receiver feeds are operator-configured and local-only.** `/api/local-receivers/aircraft` reads only the `aircraft.json` URLs in the server's `LOCAL_RECEIVER_FEEDS`; the browser never supplies an address. Each host must pass the shared tap address rule (`src/data/tapAddress.js`: loopback, RFC1918, `localhost`, `*.local`; no link-local, IPv6 or other names), the scheme must be http(s), the path must end in `aircraft.json`, and credentials, queries and fragments are refused. Invalid entries are logged at startup and never fetched. Reads use a 2 s timeout, refuse redirects, cap bodies at 2 MB and share one read per second; responses name each feed by band only and never carry upstream error text.
-- **Validated response formats.** Proxied bodies are relayed only in the format the route serves. CCTV frames and the Street View fallback accept JPEG, PNG, GIF, WebP and AVIF only, sent under their canonical type; any other type falls through to the next fallback. Live CCTV media must match its feed kind (`video/mp4`, `video/webm`, or `multipart/x-mixed-replace` with a boundary) before it is relayed or the camera counts as healthy, and its redirects stay on the registered origin. GBFS bodies must parse as JSON and are re-serialized as `application/json; charset=utf-8`. Camera catalog URLs are pinned by parsed URL — scheme, exact host, no credentials, default port, and a normalized path inside the agency's image directory — and a redirect on a pinned host must stay inside the same directory. Every `/api/cctv` route uses the keyless cross-site checks described below, so cameras stay reachable behind a reverse proxy; a request carrying forwarding headers never reaches the key-bearing Street View fallback and gets the placeholder frame instead, as when no key is configured.
+- **Validated response formats.** Proxied bodies are relayed only in the format the route serves. CCTV frames and the Street View fallback accept JPEG, PNG, GIF, WebP and AVIF only, sent under their canonical type; any other type falls through to the next fallback. The one exception is a source registered as an MJPEG still (the Taiwan Highway Bureau feeds): its `multipart/x-mixed-replace` answer is read only up to its first JPEG part, capped at 2 MB, and sent as `image/jpeg`; a multipart answer from any other camera falls through. A camera whose API needs an operator credential (the City of Ottawa certificate, `OTTAWA_CAMERA_CERTIFICATE`) has a keyless catalog URL; the frame proxy adds the credential only at fetch time, only for a URL inside that camera's pinned path, so `/api/cctv/sources` and `/api/cctv/stream` never carry it. Live CCTV media must match its feed kind (`video/mp4`, `video/webm`, or `multipart/x-mixed-replace` with a boundary) before it is relayed or the camera counts as healthy, and its redirects stay on the registered origin. GBFS bodies must parse as JSON and are re-serialized as `application/json; charset=utf-8`. Camera catalog URLs are pinned by parsed URL — scheme, exact host, no credentials, default port, and a normalized path inside the agency's image directory — and a redirect on a pinned host must stay inside the same directory. Every `/api/cctv` route uses the keyless cross-site checks described below, so cameras stay reachable behind a reverse proxy; a request carrying forwarding headers never reaches the key-bearing Street View fallback and gets the placeholder frame instead, as when no key is configured.
 - **Consistent API response headers.** Every `/api` response, including errors, partial content, Host refusals and unknown routes, carries `Content-Security-Policy: default-src 'none'; sandbox` and `X-Content-Type-Options: nosniff` (`apiResponseHeadersPlugin` in `build/vite.js`, installed ahead of the Host check). A route that sets its own policy adds it as a further policy; it never replaces this one.
 - **Response-size caps and timeouts** on proxied responses.
 - **Sanitized errors** — internal error details are not echoed back to clients.