fix: bound CCTV media bodies with an idle deadline

The media relay only deadlined the wait for upstream response headers. Once
headers arrived the timer stopped, so an upstream that answered and then sent
nothing held both the client response and the upstream socket open for as long
as the camera host allowed. The declared Content-Length ceiling was the only
body bound, and a chunked or length-less body had none.

A 30-second idle deadline now measures the gap between upstream chunks and
tears the stream down through the existing release path. Because a paused pipe
also stops upstream bytes arriving, the deadline reschedules itself whenever
the response is still waiting to drain, so a viewer on a slow link is not read
as a dead camera. Live feeds that keep delivering frames are unaffected.

server/providers/cctv/constants.js

@@ -253,5 +253,10 @@ export const CCTV_FRAME_MAX_BODY_BYTES = 16 * 1024 * 1024;
 
 /** Deadline for upstream response headers; live bodies keep streaming afterward. */
 export const CCTV_MEDIA_FETCH_TIMEOUT_MS = 15 * 1000;
+/** Silence a live body may carry before the relay gives up on it. Twice the
+ * header deadline, because a camera that is merely slow between frames is far
+ * more common than one that has died mid-stream, and a viewer would rather
+ * wait than be dropped. */
+export const CCTV_MEDIA_IDLE_TIMEOUT_MS = 30 * 1000;
 /** Declared size ceiling for fixed media responses. */
 export const CCTV_MEDIA_MAX_BODY_BYTES = 64 * 1024 * 1024;