feat: add indexer and torrent REST controllers with service layer

- Add config module for yaml config (database, indexers, torrent)
- Add indexer module with Torznab protocol support
- Add IndexerService and TorrentService for business logic
- Add REST controllers for indexer search and torrent management
- Add Docker Compose for PostgreSQL and Jackett
- Add ERD documentation for database schema

config.example.yaml

@@ -0,0 +1,13 @@
+database:
+  url: "postgresql://music:music@localhost:5433/music_aggregator"
+
+indexers:
+  - name: "Jackett"
+    url: "http://localhost:9117"
+    api_key: "your-jackett-api-key"
+
+torrent:
+  qbittorrent:
+    url: "http://localhost:8080"
+    username: "admin"
+    password: "changeme"