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>

docs/MEMORY_SYSTEM_PLAN.md

@@ -7,7 +7,7 @@ A three-tier memory architecture for Library Desk with intelligent orchestration
 | Tier | Storage | Purpose | TTL |
 |------|---------|---------|-----|
 | **Volatile** | Qdrant (vectors) | Weather, news, financial, ephemeral context | 5min - 2hr |
-| **Documents** | TBD (research) | Git mirrors, PDFs, video, images | Permanent |
+| **Documents** | Paperless-ngx + ClamAV (host) | Git mirrors, PDFs, video, images | Permanent |
 | **Knowledge** | Wiki + Neo4j | Personal dossiers, research, summaries | Permanent |
 
 **Implementation Priority**: Cleanup → Volatile → Documents → Test Data Cleanup
@@ -18,7 +18,7 @@ A three-tier memory architecture for Library Desk with intelligent orchestration
 |-------|--------|---------|
 | Phase 1: Cleanup System | ✅ Complete | v1.4.0 |
 | Phase 2: Volatile Memory | ✅ Complete | v1.4.3 |
-| Phase 3: Document Storage | ⏳ Pending | - |
+| Phase 3: Document Storage | ✅ Planned | See [DOCUMENT_STORAGE_PLAN.md](DOCUMENT_STORAGE_PLAN.md) |
 | Phase 4: Test Data Cleanup | ✅ Complete | v1.4.4 |
 
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