* feat(playlists): playlist folder model — store + pure grouping core
Local, per-server folder layer over the server's flat playlist list (the
Subsonic API has no folder concept). Adds:
- playlistFolders.ts: shared types + pure groupPlaylistsByFolder (used by
every surface), with full unit coverage.
- playlistFolderStore.ts: persisted Zustand store (create/rename/delete/
assign/collapse), per-server scoped; deleting a folder drops its
assignments so playlists fall back to ungrouped.
UI surfaces (sidebar + Playlists page) build on this in following commits.
* i18n(playlists): folder strings across all 9 locales
Adds the playlists.folders.* namespace (folder names, move/remove, expand/
collapse, group-by-folders toggle, count plurals, and the local-only notice
explaining that Navidrome and the Subsonic API have no native folder support).
* feat(playlists): folder views, drag-to-folder, move-to-folder menu, view toggle
Surfaces the local folder layer on both the Playlists page and the sidebar:
- Page: collapsible folder sections + ungrouped remainder, each reusing
VirtualCardGrid; flat grid is kept verbatim when no folders exist or the
group view is toggled off.
- Drag-to-folder via the shared mouse-based psy-drop system (HTML5 DnD is
unusable in WebKitGTK); the whole section is the drop zone, and the
ungrouped zone appears during a drag so a playlist can always return to root.
- "Move to folder" submenu in the playlist context menu (keyboard-accessible
path; also creates folders on the fly) — stays available offline.
- Header gets a "New folder" action and a "Group by folders" view toggle
(both context-aware); a notice surfaces the local-only caveat.
- Sidebar renders the same collapsible folder groups.
- groupView preference added to the folder store.
* docs(changelog): note playlist folders (#1119)
Psychotoxical