refactor: remove dead code and unused imports

- Remove unused get_default_user() from dependencies.py
- Remove unused imports from routers:
  - wiki.py: HTTPAuthorizationCredentials, Security
  - graph.py: Neo4jClient, WikiJSClient
  - hybrid_rag.py: VectorService, GraphService (duplicates)

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

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

src/core/dependencies.py

@@ -395,18 +395,6 @@ def get_rag_search_service() -> "RAGSearchService":
     )
 
 
-# Utility: Get default user from settings or multi_tenancy
-def get_default_user() -> str:
-    """
-    Get default user for operations.
-
-    Returns:
-        Default user identifier
-    """
-    from src.core.multi_tenancy import DEFAULT_USER
-    return DEFAULT_USER
-
-
 # Authentication
 from fastapi import Security, HTTPException
 from fastapi.security import HTTPBearer

src/routers/graph.py

@@ -15,8 +15,6 @@ from src.models.graph import (
     MindMapResponse
 )
 from src.services.graph_service import GraphService
-from src.clients.neo4j_client import Neo4jClient
-from src.clients.wikijs_client import WikiJSClient
 from src.core.dependencies import Neo4jDep, WikiJSDep, verify_api_key
 from src.core.multi_tenancy import DEFAULT_USER
 

src/routers/hybrid_rag.py

@@ -10,10 +10,6 @@ import logging
 
 from src.models.hybrid_rag import HybridRAGRequest, HybridRAGResponse
 from src.services.hybrid_rag_service import HybridRAGService
-from src.services.vector_service import VectorService
-from src.services.graph_service import GraphService
-from src.clients.searxng_client import SearXNGClient
-from src.clients.ollama_client import OllamaClient
 from src.core.dependencies import (
     Neo4jDep, WikiJSDep, QdrantDep, OllamaDep,
     SearXNGDep, ContentExtractorDep, verify_api_key, get_settings

src/routers/wiki.py

@@ -5,8 +5,7 @@ Endpoints for wiki page and dossier management.
 All operations are scoped to user namespaces for multi-tenancy.
 """
 
-from fastapi import APIRouter, HTTPException, Depends, Query, Security, BackgroundTasks
-from fastapi.security import HTTPAuthorizationCredentials
+from fastapi import APIRouter, HTTPException, Depends, Query, BackgroundTasks
 from typing import Optional
 import logging