fix: lazy DB engine init for CI (no DATABASE_URL in test)

Author: voidreamer

backend/app/database.py

@@ -4,19 +4,35 @@
 
 DATABASE_URL = os.environ.get("DATABASE_URL", "")
 
-engine = create_engine(DATABASE_URL, pool_pre_ping=True)
+_engine = None
+_SessionLocal = None
 
-# Set search_path to heynom schema on every new connection
-@event.listens_for(engine, "connect")
-def set_search_path(dbapi_connection, connection_record):
-    cursor = dbapi_connection.cursor()
-    cursor.execute("SET search_path TO heynom, public")
-    cursor.close()
 
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+def _get_engine():
+    global _engine
+    if _engine is None:
+        if not DATABASE_URL:
+            raise RuntimeError("DATABASE_URL not set")
+        _engine = create_engine(DATABASE_URL, pool_pre_ping=True)
+
+        @event.listens_for(_engine, "connect")
+        def set_search_path(dbapi_connection, connection_record):
+            cursor = dbapi_connection.cursor()
+            cursor.execute("SET search_path TO heynom, public")
+            cursor.close()
+
+    return _engine
+
+
+def _get_session_local():
+    global _SessionLocal
+    if _SessionLocal is None:
+        _SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=_get_engine())
+    return _SessionLocal
 
 
 def get_db():
+    SessionLocal = _get_session_local()
     db = SessionLocal()
     try:
         yield db