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/database.py

@@ -2,17 +2,33 @@ import os
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker, declarative_base
 
-SQLALCHEMY_DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///./music.db")
+# PostgreSQL connection configuration
+# Uses docker hostname 'music_db' when running in container, falls back to external IP for local dev
+POSTGRES_HOST = os.getenv("POSTGRES_HOST", "music_db")
+POSTGRES_PORT = os.getenv("POSTGRES_PORT", "5432")
+POSTGRES_USER = os.getenv("POSTGRES_USER", "bnair")
+POSTGRES_PASSWORD = os.getenv("POSTGRES_PASSWORD", "Bharath2002")
+POSTGRES_DB = os.getenv("POSTGRES_DB", "music_db")
 
-connect_args = {}
-if SQLALCHEMY_DATABASE_URL.startswith("sqlite"):
-    connect_args["check_same_thread"] = False
+# Build the PostgreSQL URL
+# Format: postgresql://user:password@host:port/database
+SQLALCHEMY_DATABASE_URL = os.getenv(
+    "DATABASE_URL",
+    f"postgresql://{POSTGRES_USER}:{POSTGRES_PASSWORD}@{POSTGRES_HOST}:{POSTGRES_PORT}/{POSTGRES_DB}",
+)
 
-engine = create_engine(SQLALCHEMY_DATABASE_URL, connect_args=connect_args)
+# PostgreSQL connection pool settings for production
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    pool_size=5,  # Maintain 5 connections in the pool
+    max_overflow=10,  # Allow up to 10 additional connections
+    pool_pre_ping=True,  # Verify connection health before using
+)
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 
 Base = declarative_base()
 
+
 def get_db():
     db = SessionLocal()
     try: