feat: restore core admin modules and harden ai model fallback

backend-fastapi/ai_platform/api/agent_api.py

@@ -16,7 +16,7 @@ from app.base_schema import PaginatedResponse, ResponseModel
 from utils.context import get_current_user_id_from_context
 from ai_platform.models import (
     Agent, AgentConversation, AgentMessage,
-    LLMModel, AIWorkflow,
+    LLMModel, LLMProvider, AIWorkflow,
 )
 from core.application.model import Application
 from ai_platform.schemas.agent_schema import (
@@ -59,10 +59,13 @@ CODEX_AGENT_PROMPT = """
 async def _resolve_default_chat_model_id(db: AsyncSession) -> Optional[str]:
     result = await db.execute(
         select(LLMModel)
+        .join(LLMProvider, LLMProvider.id == LLMModel.provider_id)
         .where(
             LLMModel.is_deleted == False,
             LLMModel.is_active == True,
             LLMModel.model_type == "chat",
+            LLMProvider.is_deleted == False,
+            LLMProvider.is_active == True,
         )
         .order_by(LLMModel.sort.desc(), LLMModel.sys_create_datetime.desc())
     )