ApiClient.buildDio takes on401; the library's dioProvider wires it to
the auth controller's clearSession. The router redirect already handles
navigation away from authed screens once the session goes null.
HomeScreen surfaces the banner on connection_refused with Retry +
Change URL.
LikedIdsController loads /api/likes/ids once and mutates the local set
on toggle. Failed mutations roll the set back so the icon never lies.
Wired into ArtistDetail header, AlbumDetail header, and per-track in
the album track list.
LibraryApi wraps GET /api/home, /api/artists/{id}(/tracks),
/api/albums/{id}. dioProvider builds an authenticated dio (token
resolver reads session_token from secure storage on every request).
homeProvider, artistProvider(id), albumProvider(id) sit on top.
Login uses a non-authenticated dio (token resolver returns null) since
we don't have one yet. On success, setSession persists token + user
into secure storage and the AuthController state flips, which the
router watches to navigate.
AuthController is an AsyncNotifier holding the currently-logged-in
User. server_url, session_token, current_user all live in
flutter_secure_storage. ServerUrlScreen probes /healthz before saving
the URL so we don't store a bogus base.
ApiError.fromDio handles both server envelope shapes: {"error":"code"}
(admin endpoints) and {"error":{"code","message"}} (most others). Same
dual-shape problem the web apiFetch already solves. Token comes from a
resolver function so the auth provider can swap implementations
without touching the client.
ErrorCopy is a lazy singleton over assets/error-copy.json with the
same fallback chain web uses (specific code -> unknown -> hard-coded).
bvandeusen