Closes the Flutter half of Fable #416. Web got a generalized
system-playlist refresh kebab in d12afda; this brings Flutter to
parity instead of leaving the affordance web-only.
- PlaylistsApi.refreshSystem(variant): POST
/api/playlists/system/{for-you|discover}/refresh, maps the
underscore model variant to the hyphenated route segment,
returns the rotated playlist id.
- PlaylistCard: top-right PopupMenuButton on system playlists
with a context-labelled "Refresh For You" / "Refresh Discover"
item. Calls refreshSystem, invalidates playlistsListProvider
(which reconciles the rotated UUID + new tracks), snackbars
the result. ScaffoldMessenger captured pre-await.
- Tests: kebab present for system, absent for user playlists.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Mirrors the web equivalents at the same ~176dp width so the home
Playlists row keeps visual rhythm whether the slot is filled with a
real playlist or a placeholder.
PlaylistPlaceholderCard variants:
- building: spinner + "Building…"
- failed: warning + "Couldn't generate"
- seed-needed: muted icon + "Like more music"
- pending: muted icon + "Coming soon"
Used in the next commit's home Playlists row; otherwise unused this
slice.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen