Initial commit: Veeam multi-instance monitoring dashboard

- FastAPI backend with CRUD for Veeam instances
- Veeam REST API client supporting v9.5-v13 (legacy + OAuth2)
- Multi-version detection and auth fallback
- SQLite caching layer
- Web dashboard with summary cards, instance list, detail tabs
- Docker packaging

.gitignore

@@ -0,0 +1,8 @@
+__pycache__/
+*.pyc
+.venv/
+venv/
+*.db
+.env
+.DS_Store
+*.tar.gz