fix: WS5 hazards batch - CORS, scheduler auth, reranker dedupe, wiring, write txns

- CORS: drop allow_credentials (wildcard origin + credentials told
  browsers to attach credentials for any site); origins configurable via
  CORS_ALLOW_ORIGINS (default * is safe without credentials). Verified
  live: preflight no longer advertises access-control-allow-credentials.
- Scheduler tasks: auth moved from a plain Authorization header (which
  the Scheduler's rest_api_executor does NOT env-substitute) to its
  auth {type: bearer, token: ${LIBRARY_API_KEY}} block, substituted from
  the Scheduler's own environment at execution time. The registrar no
  longer resolves the real key client-side, so it can never be persisted
  into the scheduled_tasks.config JSONB column. Also fixed: JSON bodies
  moved from the ignored "body" key to "payload" (the executor only
  reads config["payload"], so the tasks would have POSTed empty bodies
  and failed required-user validation).
- Reranker: parsed ranking indices are deduplicated preserving first
  occurrence (an LLM answer like "3,3,1" duplicated a result).
- HybridRAG wiring consolidated into dependencies.get_hybrid_rag_service
  (now including volatile_service); the inline copies in /query/hybrid
  and /wiki/pages/smart-create are gone - smart-create previously ran
  without the volatile leg, and the singleton was unused.
- Remaining Neo4j writes (GraphService ingestion/deletes/purges/entity
  mentions, webhook rename+delete cleanup, document-sync _index_graph,
  consolidation mark-processed/add-entity) moved from auto-commit
  execute_query to execute_write managed transactions with retry.

Verified end-to-end on the local dev server as llm_tester: /query/hybrid
200 with all five legs ok (volatile now active), background persistence
landed as one transaction.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QbFZyDvYksazX6nYQYZ67L

src/core/dependencies.py

@@ -718,7 +718,14 @@ def get_ingestion_service() -> "IngestionService":
 
 @lru_cache
 def get_hybrid_rag_service() -> "HybridRAGService":
-    """Get HybridRAGService singleton."""
+    """
+    Get HybridRAGService singleton.
+
+    The single wiring point for HybridRAG — routers must depend on this
+    instead of constructing their own instance (previous inline copies in
+    the /query/hybrid and /wiki/smart-create routers diverged on
+    volatile_service).
+    """
     from src.services.hybrid_rag_service import HybridRAGService
     return HybridRAGService(
         vector_service=get_vector_service(),
@@ -726,7 +733,8 @@ def get_hybrid_rag_service() -> "HybridRAGService":
         searxng_client=get_searxng_client(),
         ollama_client=get_ollama_client(),
         content_extractor=get_content_extractor(),
-        settings=get_settings()
+        settings=get_settings(),
+        volatile_service=get_volatile_cache_service()
     )