Fix worker getting stuck during sync: add timeouts, stuck detection, and safety limits

- Add invokeWithTimeout wrapper for TDLib API calls (2min timeout per call)
- Add stuck detection to getChannelMessages: break if from_message_id doesn't advance
- Add stuck detection to getTopicMessages: same protection for topic scanning
- Add stuck detection to getForumTopicList: break if pagination offsets don't advance
- Add max page limit (5000) to all scanning loops to prevent infinite pagination
- Add mutex wait timeout (30min) to prevent indefinite blocking when holder hangs
- Add cycle timeout (4h default, configurable via WORKER_CYCLE_TIMEOUT_MINUTES)
- Fix end-of-page detection to use actual limit value instead of hardcoded 100

Co-authored-by: xCyanGrizzly <53275238+xCyanGrizzly@users.noreply.github.com>

worker/dist/util/mutex.d.ts

@@ -0,0 +1,8 @@
+/**
+ * Ensures only one TDLib client runs at a time across the entire worker process.
+ * Both the scheduler (auth, ingestion) and the fetch listener acquire this
+ * before creating any TDLib client.
+ *
+ * Includes a wait timeout to prevent indefinite blocking if the current holder hangs.
+ */
+export declare function withTdlibMutex<T>(label: string, fn: () => Promise<T>): Promise<T>;