Backend: /api/channels (list + PATCH priority/hidden + attach/detach user tags),
user-tag CRUD on /api/tags, /api/sync/my-status (per-user channel sync counts).
Frontend: feed|channels page nav (URL-synced) from the account menu; a slide-in
tabbed Settings panel (Appearance, Notifications=6b sound+duration, Sync status +
actions + admin pause/resume, Account); a channel manager with priority, hide,
per-channel user tags, sync badges and 'view in feed'. Notifications now honor the
configurable sound + auto-dismiss settings.
Serialize the active filters to a compact, readable query string (only non-default
values) and parse them back on load, with URL taking precedence over localStorage.
Uses history.replaceState so it never spams browser history. A pasted link now
reproduces the exact view.
