fix(cctv): cap buffered snapshot downloads

Adapt the streamed snapshot size cap contributed in public PR #82 to the CCTV media module.

server/providers/cctv/constants.js

@@ -38,3 +38,6 @@ export const CCTV_SOURCE_FETCH_TIMEOUT_MS = 15 * 1000;
  * client refresh cadence. A bounded miss can fall through to Street View or
  * the synthetic frame instead of leaving the browser preview pending. */
 export const CCTV_FRAME_FETCH_TIMEOUT_MS = 8 * 1000;
+
+/** Maximum buffered snapshot size. */
+export const CCTV_FRAME_MAX_BODY_BYTES = 16 * 1024 * 1024;