Miniflux 2.2.19 + container.py migration + ty typechecker (#331)

## Summary

- Upgrade miniflux from 2.2.17 to 2.2.19 (security hardening, performance improvements)
- Migrate miniflux from Dockerfile to native Dagger container.py build
- Refactor `alpine_runtime()` helper to support existing users (nobody/65534)
- Add `ty` (Astral) Python typechecker to prek hooks

## Test plan

- [ ] `dagger call build --src=. --container-name=miniflux` succeeds
- [ ] `dagger call container-version --container-name=miniflux` returns 2.2.19
- [ ] `mise run container-version-check` passes
- [ ] `ty check` passes cleanly
- [ ] `prek run --all-files` passes
- [ ] CI builds container successfully
- [ ] Miniflux healthcheck passes after deploy from branch

Reviewed-on: #331

pyproject.toml

@@ -10,3 +10,10 @@ build-backend = "uv_build"
 
 [tool.uv.sources]
 dagger-io = { path = "sdk", editable = true }
+
+[tool.ty.environment]
+python-version = "3.13"
+extra-paths = ["sdk/src"]
+
+[tool.ty.src]
+exclude = ["pulumi/", "containers/transmission-exporter/"]