Native Dagger container builds + Navidrome v0.61.1 (#330)

## Summary
- Move Dagger module from `.dagger/` to repo root (`src/blumeops/`), rename `blumeops-ci` → `blumeops`
- Replace opaque `docker_build()` with native Dagger pipelines that surface full build errors per step
- Migrate navidrome as the first container (`containers/navidrome/container.py`)
- Upgrade navidrome from v0.60.3 to v0.61.1 (major artwork overhaul, SQLite FTS5 search, server-managed transcoding)
- Add `dagger call container-version` for CI version extraction without Dockerfile parsing
- All mise tasks (`container-list`, `container-version-check`, `container-build-and-release`) updated for hybrid mode
- Legacy `docker_build()` fallback preserved for all other containers

## Motivation
When navidrome v0.61.0 added a new Go build tag (`sqlite_fts5`), `docker_build()` showed only "exit code: 1". We had to run `docker build --progress=plain` manually to find `undefined: buildtags.SQLITE_FTS5`. Native Dagger pipelines show the full error inline.

## Container build dispatch needed
After merge, dispatch container build for navidrome:
```
mise run container-build-and-release navidrome --ref 470b4bd
```

## Deploy steps
1. Wait for container build to complete
2. Back up navidrome-data PVC (non-reversible DB migrations)
3. `argocd app set navidrome --revision main && argocd app sync navidrome`
4. Verify at https://dj.ops.eblu.me

## Future
Remaining containers migrate incrementally in follow-up PRs using the same pattern.

Reviewed-on: #330

docs/how-to/knowledgebase/review-services.md

@@ -47,6 +47,7 @@ For all service types, start by reading the service's reference card (`docs/refe
 3. Review the upstream changelog for breaking changes
 4. If the service uses a custom-built container, also check the base image for security updates and follow [[build-container-image]] to rebuild
 5. If upgrading, update the manifest and follow [[deploy-k8s-service]]
+6. If the container still uses a Dockerfile (no `container.py`), consider migrating to a native Dagger build — see the `containers/navidrome/container.py` pattern for reference
 
 ### Ansible Services (`type: ansible`)