feat: integrate message capture into bot startup

- Register message capture handlers on bot ready
- Export getDatabase function from muxer-queue
- Initialize database schema for messages and attachments

src/muxer-queue.ts

@@ -55,6 +55,8 @@ function getDatabase(): Database.Database {
   return db;
 }
 
+export { getDatabase };
+
 export async function enqueueMuxerJob(data: MuxerJobData): Promise<string> {
   try {
     const database = getDatabase();