add tidb spend limit config (#9999)

api/configs/middleware/vdb/tidb_on_qdrant_config.py

         description="Tidb project id",
         default=None,
     )
+
+    TIDB_SPEND_LIMIT: Optional[int] = Field(
+        description="Tidb spend limit",
+        default=100,
+    )

api/core/rag/datasource/vdb/tidb_on_qdrant/tidb_service.py

 import requests
 from requests.auth import HTTPDigestAuth
 
+from configs import dify_config
 from extensions.ext_database import db
 from extensions.ext_redis import redis_client
 from models.dataset import TidbAuthBinding
             }
 
             spending_limit = {
-                "monthly": 10,
+                "monthly": dify_config.TIDB_SPEND_LIMIT,
             }
             password = str(uuid.uuid4()).replace("-", "")[:16]
             display_name = str(uuid.uuid4()).replace("-", "")