api: replace fever with miniflux v1 api
Hard cutover from Fever API to Miniflux-compatible v1 API with
DB as source of truth for categories/feeds/items.
* add migrations for items.is_starred and items.changed_at
* remove fever handler, routes, and all fever tests
* replace destructive sync_config with one-time legacy bootstrap
that only imports from config when DB is empty
* add miniflux auth middleware (X-Auth-Token + HTTP Basic)
* implement full miniflux endpoint surface: categories/feeds/entries
CRUD, counters, icons, OPML export, bookmarks, health, version
* add broadcast channel for manual feed refresh triggers
* replace CLI auth/add commands with token generator and DB-based
OPML import
* add 30 integration tests covering auth, CRUD, filtering, and
status updates
Co-authored-by: Claude <noreply@anthropic.com>