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/config.py

@@ -95,6 +95,18 @@ class Settings(BaseSettings):
     app_version: str = Field(default=__version__, description="Application version")
     debug: bool = Field(default=False, description="Debug mode")
 
+    # CORS: comma-separated list of allowed browser origins. The default "*"
+    # is only acceptable because allow_credentials is disabled (see main.py).
+    cors_allow_origins: str = Field(
+        default="*",
+        description="Comma-separated CORS allowed origins (credentials are never allowed)"
+    )
+
+    @property
+    def cors_allow_origins_list(self) -> list[str]:
+        """cors_allow_origins parsed into a list for CORSMiddleware."""
+        return [o.strip() for o in self.cors_allow_origins.split(",") if o.strip()]
+
     # RAG Search Configuration
     search_cache_ttl: int = Field(default=300, ge=0, le=3600, description="Search cache TTL in seconds")
     search_timeout: int = Field(default=10, ge=1, le=60, description="SearXNG timeout in seconds")