feat: migrate to PostgreSQL and enhance playlist curation

- Migrate database from SQLite to PostgreSQL (100.91.248.114:5433)
- Fix playlist curation to use actual top tracks instead of AI name matching
- Add /playlists/history endpoint for historical playlist viewing
- Add Playlist Archives section to frontend with expandable history
- Add playlist-modify-* scopes to Spotify OAuth for playlist creation
- Rewrite Genius client to use official API (fixes 403 scraping blocks)
- Ensure playlists are created on Spotify before curation attempts
- Add DATABASE.md documentation for PostgreSQL schema
- Add migrations for PlaylistConfig and composition storage

backend/app/models.py

@@ -130,3 +130,18 @@ class AnalysisSnapshot(Base):
     daily_playlist_id = Column(
         String, nullable=True
     )  # Spotify playlist ID for 24-hour playlist
+    playlist_composition = Column(JSON, nullable=True)
+    playlist_composition = Column(
+        JSON, nullable=True
+    )  # Store the track list at this snapshot
+
+
+class PlaylistConfig(Base):
+    __tablename__ = "playlist_config"
+
+    key = Column(String, primary_key=True, index=True)  # e.g., "six_hour", "daily"
+    spotify_id = Column(String, nullable=False)
+    last_updated = Column(DateTime, default=datetime.utcnow)
+    current_theme = Column(String, nullable=True)
+    description = Column(String, nullable=True)
+    composition = Column(JSON, nullable=True)