Fix schema init: use psycopg2 directly to bypass SQLAlchemy param parsing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/main.py

@@ -29,19 +29,23 @@ from scheduler import start_scheduler, shutdown_scheduler
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     # Apply database schema (idempotent CREATE TABLE IF NOT EXISTS)
-    # Uses exec_driver_sql to bypass SQLAlchemy parameter parsing — schema.sql
-    # contains PL/pgSQL with $1/$2 syntax that text() misinterprets as bindparams.
+    # Uses psycopg2 directly — schema.sql contains PL/pgSQL with $1/$2 syntax
+    # that SQLAlchemy text() misinterprets as bindparams.
     try:
-        import os
-        from database import sync_engine
+        import os, psycopg2
+        from database import DATABASE_URL
         schema_path = os.path.join(os.path.dirname(__file__), 'schema.sql')
         if os.path.exists(schema_path):
             with open(schema_path) as f:
                 sql = f.read()
-            with sync_engine.connect() as conn:
-                conn.exec_driver_sql(sql)
-                conn.commit()
+            conn = psycopg2.connect(DATABASE_URL)
+            try:
+                conn.autocommit = True
+                with conn.cursor() as cur:
+                    cur.execute(sql)
                 logging.getLogger(__name__).info("Schema applied successfully")
+            finally:
+                conn.close()
     except Exception as e:
         logging.getLogger(__name__).warning(f"Schema init failed: {e}")