feat: add Paperless-ngx document storage integration

- Add /documents router with webhook, upload, search, health endpoints
- Create DocumentSyncService for indexing documents to vectors/graph
- Add PaperlessClient for REST API integration
- Configure dependency injection for Paperless client
- Add document models for webhook payloads and responses
- Event-driven architecture via Paperless workflow webhooks

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

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

.env.example

@@ -7,6 +7,7 @@ QDRANT_PORT=6333
 OLLAMA_URL=http://192.168.86.149:11434
 SEARXNG_URL=http://192.168.86.149:8080
 REDIS_HOST=192.168.86.149
+PAPERLESS_URL=http://192.168.86.149:8000
 
 OLLAMA_MODEL=mistral-nemo-large:latest
 OLLAMA_EMBEDDING_MODEL=nomic-embed-text
@@ -20,4 +21,5 @@ WIKI_GRAPHQL_API=your_jwt_token_here
 LIBRARY_API_KEY=key_here
 NEO4J_PASSWORD=key_here
 WIKIJS_DB_PASSWORD=key_here
-SCHEDULER_API_KEY=key_here
+SCHEDULER_API_KEY=key_here
+PAPERLESS_TOKEN=key_here