Backport langgenius/dify#35158 to hotfix branch: persist a per-cluster
qdrant endpoint on TidbAuthBinding so each tenant connects to the
qdrant gateway colocated with its TiDB Serverless cluster instead of a
single global TIDB_ON_QDRANT_URL, which fails for clusters in other
regions.
Adapted to the hotfix branch's pre-monorepo paths
(api/core/rag/datasource/vdb/tidb_on_qdrant/) and direct httpx usage.
Made-with: Cursor