Ensure foreign key constraints are always enforced

mft/database.py

@@ -20,6 +20,7 @@ def get_db() -> Generator[sqlite3.Connection, None, None]:
     """Get a database connection context manager."""
     conn = sqlite3.connect(settings.database_path)
     conn.row_factory = sqlite3.Row  # Enable dict-like access to rows
+    conn.execute("PRAGMA foreign_keys = ON")
     try:
         yield conn
     finally: