Record sent chats in messages repo and blur gallery by default

Threads MessagesRepository through ChatService so first outgoing chat
messages are persisted for stats, and extends the repo + DB client to
support chat-room-keyed lookups. Adds tests covering the new behavior.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/bootstrap.ts

@@ -206,6 +206,8 @@ export async function bootstrap(config: Config, logger: Logger): Promise<AppCont
     mediaService,
     tokenRefresher,
     usernameResolver,
+    undefined,
+    messagesRepo,
   );
 
   const mediaSyncService = new MediaSyncService(chatService, logger, config.media.syncIntervalMs);