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/main.py

@@ -39,11 +39,18 @@ app = FastAPI(
     redoc_url="/redoc",
 )
 
-# CORS middleware
+# CORS middleware.
+# allow_credentials is deliberately False: combined with a wildcard origin it
+# would tell browsers to attach cookies/credentials for ANY site, which is the
+# classic CORS misconfiguration. All real callers (tatlock, the Scheduler) are
+# server-to-server and use the Authorization header, which wildcard-origin
+# CORS without credentials still permits. Origins can be restricted via the
+# CORS_ALLOW_ORIGINS env (comma-separated) once a cross-origin browser UI
+# exists; the bundled static UI is served same-origin and needs no CORS.
 app.add_middleware(
     CORSMiddleware,
-    allow_origins=["*"],  # Configure appropriately for production
-    allow_credentials=True,
+    allow_origins=get_settings().cors_allow_origins_list,
+    allow_credentials=False,
     allow_methods=["*"],
     allow_headers=["*"],
 )