feat: add maintenance system with index reconciliation

Complete maintenance subsystem for index health and cleanup:

Endpoints:
- GET /maintenance/health - lightweight (or detailed) health check
- POST /maintenance/cleanup/all - full orphan cleanup
- POST /maintenance/cleanup/vectors - purge orphan vector chunks
- POST /maintenance/cleanup/graph - purge orphan graph nodes
- POST /maintenance/reconcile-index - cleanup + reindex missing pages

Bidirectional orphan detection:
- find_documents_without_vectors() in GraphService
- find_chunks_without_graph_nodes() in VectorService

Redis integration:
- Tracks last_cleanup timestamp for scheduler visibility

Config additions:
- Document store, volatile cache, and maintenance settings
- VectorServiceDep and GraphServiceDep type aliases

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/core/dependencies.py

@@ -76,13 +76,12 @@ def get_wikijs_client() -> WikiJSClient:
     Get Wiki.js client singleton.
 
     Returns:
-        Initialized Wiki.js GraphQL client with username/password auth
+        Initialized Wiki.js GraphQL client with API token auth
     """
     settings = get_settings()
     client = WikiJSClient(
         base_url=settings.wikijs_url,
-        username=settings.wikijs_username,
-        password=settings.wikijs_password
+        api_token=settings.wiki_graphql_api
     )
     logger.debug("Created Wiki.js client instance")
     return client
@@ -425,3 +424,12 @@ async def verify_api_key(
             detail="Invalid API key"
         )
     return credentials.credentials
+
+
+# Service type aliases for FastAPI endpoint dependencies
+# These are defined after the factory functions
+from src.services.vector_service import VectorService
+from src.services.graph_service import GraphService
+
+VectorServiceDep = Annotated[VectorService, Depends(get_vector_service)]
+GraphServiceDep = Annotated[GraphService, Depends(get_graph_service)]