fix: address review on Kartverket ground heights

- Send 20 points per request, not 50: above ~20 Kartverket answers the
  extra points from contour lines (hoydekurver) or not at all. At 20,
  nearly every camera resolves from dtm1, so the null-retry pass is gone.
  Eight requests in flight keep a cold lookup ~6 s.
- Cache misses: positions with no height are not asked again for 6 h.
- Transport failures: the first 429, 5xx or network error stops the
  lookup with no retries, and no lookup starts until the backoff ends
  (Retry-After when sent, else 10 min; bounded to 1 min-1 h).
- Budget the 12 s wait from the start of the loader, catalog fetch
  included.
- Record answers only for the points each request asked about.
- Send the CCTV User-Agent; link CC BY 4.0 in the credit.
- Docs: bridge cameras sit at the water surface, below the deck.
- Tests: batching, 8-in-flight cap, request count on failure, the shared
  deadline, Retry-After bounds, null TTL, backoff, the -20 m bound and
  each water marker on its own.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

DATA_SOURCES.md

@@ -91,7 +91,7 @@ The optional Local ADS-B layer and the broadcast-FM receiver use radio you recei
 - **Live Traffic NSW cameras.** The camera list is the keyless public `data.livetraffic.com/cameras/traffic-cam.json` feed (Transport for NSW open data, CC BY 4.0); frames are stills on `webcams.transport.nsw.gov.au`, and only that host is registered. That image host answers non-browser clients with an HTML placeholder, so the proxy identifies as a browser for that one host and as itself everywhere else. Frames are fetched at request time and never stored or redistributed. Disable with `CCTV_NSW_ENABLED=0`.
 - **Open Calgary traffic cameras.** Keyless. The camera list is the public Socrata dataset `k7p9-kppz` on `data.calgary.ca`; frames are stills on the city's own `trafficcam.calgary.ca` host, and only that host is registered. Most rows publish an `http://` frame URL and the host redirects those to HTTPS, so URLs are upgraded and pinned to that origin before registration. Frames are fetched at request time and never stored or redistributed. The dataset publishes no camera facing: the `quadrant` field and the quadrant suffix on each camera name are Calgary's address grid, not a bearing, so headings use the shared id-hash fallback at low confidence and are corrected with the in-app calibration gizmo. The licence requires the attribution statement above. Disable with `CCTV_CALGARY_ENABLED=0`.
 - **Statens vegvesen road cameras.** Keyless. The camera list is one GeoJSON request to the OGC API Features view of the official DATEX 3.1 CCTV site table (`ogckart-sn1.atlas.vegvesen.no/ogc/features/v1/collections/datex_3_1:CctvSimple/items`), so no DATEX account is needed; frames are stills on `kamera.atlas.vegvesen.no/api/images/<cameraId>`, and only that exact path per camera is registered. Cameras the feed reports as faulty are dropped. About 135 working cameras also publish live HLS (`kamera.vegvesen.no/public/<cameraId>/manifest.m3u8`, MPEG-TS); those play as live video through the bounded in-memory HLS relay, with the still as the snapshot fallback, and only that exact manifest path per camera is registered. `CCTV_VEGVESEN_VIDEO=0` keeps every camera on stills. `orientationDescription` names the place a camera faces, not a bearing, so it goes into the label and headings use the id-hash fallback at low confidence. By default every live camera loads (~850); `CCTV_VEGVESEN_MAX_SOURCES` (8–1000) lowers the cap, keeping the cameras nearest Oslo, Bergen, Stavanger, Trondheim, Kristiansand, Bodø and Tromsø and `CCTV_VEGVESEN_ENABLED=0` turns the pack off. Frames are fetched at request time and never stored or redistributed. The NLOD attribution is registered in the Data attribution popover.
-- **Kartverket ground heights for Statens vegvesen cameras.** The camera feed's points are 2D, so the loader asks Kartverket's keyless point-height API (`ws.geonorge.no/hoydedata/v1/punkt`, CC BY 4.0) for the terrain height at each camera, 50 points per request with up to six in flight (about 17 requests, ~5 s, for the whole country). Points a full batch answers `null` for are retried once in batches of 10, since the API sometimes drops points from large batches; points still without data keep the flat 150 m prior. Over water the API returns the sea-floor depth (`dybdekurver` / `Havflate`), which is replaced by 0 m, the water surface. Heights are cached in memory by position, so the 15-minute catalog refresh only asks about new or moved cameras. A catalog load waits at most 12 s; a slower lookup keeps filling the cache for the next refresh. Only coordinates are sent. `CCTV_VEGVESEN_HEIGHTS=0` turns the lookup off. The Kartverket credit is shown beside the Statens vegvesen entry in the Data attribution popover.
+- **Kartverket ground heights for Statens vegvesen cameras.** The camera feed's points are 2D, so the loader asks Kartverket's keyless point-height API (`ws.geonorge.no/hoydedata/v1/punkt`, CC BY 4.0) for the terrain height at each camera. Requests carry 20 points: the API accepts 50, but above ~20 it answers the extra points from contour lines (`hoydekurver`, metres to ~20 m off) or not at all. Eight requests run at a time, about 36 for the whole country (~6 s). Answers are matched by the coordinates the API echoes and recorded only for points that request asked about. Over water the API returns the sea-floor depth (`dybdekurver` or `Havflate`), which is replaced by 0 m, the water surface; for the ~14 bridge cameras that is below the deck, but much closer than the sea floor or the flat prior. Heights are cached in memory by position for the life of the server, and points with no height (a few ferry quays and bridges) for 6 h, so the 15-minute catalog refresh only asks about new or moved cameras. The first 429, 5xx or network failure stops the lookup, with no retries, and no new lookup starts until the backoff ends (Retry-After when sent, else 10 min; bounded to 1 min–1 h). The lane waits at most 12 s, counted from the start of the loader; a slower lookup keeps filling the cache for the next refresh. Only coordinates are sent, with the same User-Agent as the other CCTV requests. `CCTV_VEGVESEN_HEIGHTS=0` turns the lookup off. The Kartverket credit is shown beside the Statens vegvesen entry in the Data attribution popover.
 - **Camera frame content.** Public camera frames can contain people, vehicles and license plates, and the camera layer does nothing with them beyond putting them on the map. A successful upstream response is relayed as the provider served it: nothing in the camera pipeline blurs, redacts, enhances or restores it, and nothing there runs face, plate or object detection or otherwise recognises or classifies what is in the picture. (The ALPR layer described below maps where plate-reader cameras are, from locations contributors tagged in OpenStreetMap; it reads nothing from any camera frame.) When an upstream has no frame for a camera, what you see instead is a Google Street View still or the app's own placeholder card; the panel's source badge names which of them you are looking at, and a refresh that fails after a frame has arrived leaves the last good picture on screen rather than replacing it. The browser resamples each frame for display: onto a fixed 1920x1080 surface for the camera's projection plane in the scene, and onto a 192x108 canvas for the small ambient card. That scaling is the only change made to the picture, and the only pixels the camera layer reads back are a 64x36 downscale hashed to tell whether the picture has changed. Live streams are piped through; the still path reads the image into memory to pass it on — TxDOT wraps its JPEG in a JSON envelope, which is decoded there — and no frame is written to disk (the disk cache, `.gev-cache/`, holds feed JSON for other layers and never camera imagery). Outside that pipeline, the voice assistant is the one feature that sends imagery anywhere: when it answers a question about what is in view it may attach a downscaled screenshot of the rendered scene — including any camera plane on screen — to the request it sends to the voice model. Frames are fetched only from server-registered camera URLs — a client cannot hand the proxy a URL (see [SECURITY.md](SECURITY.md)). What the app does stays inside the line README draws: no named-person search, no face recognition, no tracking individuals.
 - **Transit (GTFS-Realtime).** The proxy requests only registered operator feeds, validates redirects, bounds responses, and uses conditional requests, short snapshot caching and failure backoff. All seven registered regions are live-enabled; each can be disabled independently. Vehicles use delayed playback between reports, with report age and waiting states shown separately. Session-local selected trails are available for every feed. MBTA additionally retains up to 15 minutes of recently observed positions in the running proxy, so available history can survive a browser reload; server restart clears it. History reads never fetch upstream, and other feeds have no proxy retention. Nothing is archived to disk or collected in the background. Operator text credits are included as a courtesy and do not imply endorsement. Heights are aligned to work with Google 3D tiles; subway markers are shown at street level because these feeds do not supply depth.
 - **Radio Browser.** `/api/radio/stations` discovers official API mirrors, makes bounded and coalesced healthy/geolocated HTTPS-station queries, caches the normalized public-domain directory for 45 minutes, and may serve the last good catalog for up to seven days during an outage. Refreshes must meet minimum accepted-query and station coverage before replacing a warm catalog; schema-valid responses whose rows all fail the product's health policy do not count as successful queries. A usable partial cold catalog is explicitly `DEGRADED`, and malformed or empty successful payloads are rejected atomically. Every directory and click-count request rejects redirects, validates all resolved addresses as globally routable (including reserved/documentation IPv4 and special/non-global IPv6 exclusions), and pins the TLS connection to a validated address. Only MP3/AAC non-HLS directory rows with public HTTPS stream targets are returned; favicons are intentionally omitted. Pressing play connects one browser audio element directly to the selected broadcaster and calls the directory's click counter through known-ID-only `POST /api/radio/click/:uuid`. GEV never proxies, caches, records, bundles, or redistributes audio. Radio Browser supplies station-level tags, not dependable current-song or upcoming-program metadata, so Radio filtering never claims either. Direct playback exposes the listener's IP address to the broadcaster, whose own stream terms apply.