fix(control-pipeline): anchor finder uses direct Qdrant search instead of Go SDK

The Go SDK RAG proxy returns 401 (Qdrant API key mismatch). Switch
AnchorFinder to use direct Qdrant vector search + embedding service,
same approach as the main pipeline. No dependency on Go SDK anymore.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

control-pipeline/api/control_generator_routes.py

@@ -1125,8 +1125,7 @@ async def _run_anchor_backfill(req: AnchorBackfillRequest, backfill_id: str):
 
     db = SessionLocal()
     try:
-        rag_client = get_rag_client()
-        finder = AnchorFinder(rag_client=rag_client)
+        finder = AnchorFinder()
 
         # Find controls without anchors
         states = "('draft', 'needs_review')" if req.include_needs_review else "('draft',)"