feat(pipeline): MC Quality Overhaul — 74.5% → 92.8% accuracy, 5.3K → 13.6K MCs

Phase 0: Quality Audit script (Claude Sonnet, 1750 samples)
Phase 1: Object ontology expanded 31 → 74 tokens with descriptions + boundaries
Phase 2: 174K controls re-classified via Haiku (10 batches, $50)
  - Generic tokens removed (documentation, procedure, process)
  - L2 sub-topics added (108K + 64K controls)
  - Bad subtopics fixed (stakeholder_*, escalation fragments)
Phase 3: Re-clustering K=18704 (37K objects → 16.7K groups)
Phase 4: Direct MC generation from canonical tokens (gpre2_direct_mc.py)
Phase 5: Regulation-source split (gpre3, dry-run tested)

New features:
- Tenant-isolated document upload API (rag-service)
- BAuA crawler (Playwright, 131 PDFs downloaded)
- OSHA Technical Manual crawler (23 chapters)
- CE obligation extractor (6141 obligations from Qdrant)

RAG ingestion:
- 126 BAuA PDFs (TRBS/TRGS/ASR): 27,664 chunks
- OSHA Technical Manual: 7,241 chunks
- OSHA 1910 Subpart O (full): 745 chunks
- EuGH C-588/21 P: 216 chunks
- EU 2018/1725: 842 chunks

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

rag-service/minio_client_wrapper.py

@@ -122,6 +122,16 @@ class MinioClientWrapper:
             logger.error("Failed to delete '%s': %s", object_name, exc)
             raise
 
+    async def delete_by_prefix(self, prefix: str) -> int:
+        """Remove all objects under a prefix."""
+        objects = self.client.list_objects(settings.MINIO_BUCKET, prefix=prefix, recursive=True)
+        count = 0
+        for obj in objects:
+            self.client.remove_object(settings.MINIO_BUCKET, obj.object_name)
+            count += 1
+        logger.info("Deleted %d objects with prefix '%s'", count, prefix)
+        return count
+
     # ------------------------------------------------------------------
     # Presigned URL
     # ------------------------------------------------------------------