Pin camera sources by parsed URL

Camera catalog image URLs were pinned by string prefix, so a URL that only
began with the agency's directory before dot segments or an encoded separator
were resolved still counted as inside it. The pin now parses the URL and
requires the same scheme, the exact host, no credentials, the default port and
a normalized path inside the pinned directory. Redirects on a pinned host must
stay inside the same directory.

Document the response format checks and API response headers alongside the
existing server hardening notes.

SECURITY.md

@@ -69,6 +69,8 @@ The data proxies under `server/providers/` are written so the browser cannot tur
 - **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 cross-site gate below.
+- **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.
 - **Coalesced OAuth refresh** and cached successful responses only (OpenSky).