Fix: user_default_llm configuration doesn't work for OpenAI API compatible LLM factory (#8502)

### What problem does this PR solve?

https://github.com/infiniflow/ragflow/issues/8467
when add llm the llm_name will like "llm1___OpenAI-API"
f09ca8e795/api/apps/llm_app.py (L173)
so we should not use llm1 to query


### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/db/services/llm_service.py

@@ -45,6 +45,18 @@ class TenantLLMService(CommonService):
             objs = cls.query(tenant_id=tenant_id, llm_name=mdlnm)
         else:
             objs = cls.query(tenant_id=tenant_id, llm_name=mdlnm, llm_factory=fid)
+
+        if (not objs) and fid:
+            if fid == "LocalAI":
+                mdlnm += "___LocalAI"
+            elif fid == "HuggingFace":
+                mdlnm += "___HuggingFace"
+            elif fid == "OpenAI-API-Compatible":
+                mdlnm += "___OpenAI-API"
+            elif fid == "VLLM":
+                mdlnm += "___VLLM"
+                
+            objs = cls.query(tenant_id=tenant_id, llm_name=mdlnm, llm_factory=fid)
         if not objs:
             return
         return objs[0]