UI polish pass: library sorting, empty states, Now Playing queue, playlist covers

[EnesYilmazcode]

General UI improvement pass. Each item is independent and small enough to land separately; all grounded in current components.

Library (src/components/LibraryView.jsx)

• Sort control next to the All/Favorites segmented control: Recently added / Most played / A–Z. The data already exists on every track (dateAdded, playCount are even indexed in db.js) — this is pure UI
• Real empty state: today an empty library is just a dim text line (LibraryView.jsx:50). Replace with a centered empty state: icon, one-line explanation of the Files→Import flow, and a prominent Import button (reuse ImportButton)
• Track count + total duration under the header ("42 songs · 2 hr 51 min")

Now Playing (src/components/Player.jsx)

• Queue view: no way to see or reorder what plays next. Add a third panel (alongside artwork/lyrics) listing the current queue with the active track highlighted; tap to jump, drag to reorder
• Swipe-down to dismiss the full-screen sheet (currently only the chevron button closes it) — standard iOS player gesture
• Mini bar: swipe left/right for next/previous (long-press infra in useLongPress.js shows the touch-handling pattern to follow; ensure no conflict with tap-to-expand)

Playlists (src/components/PlaylistsView.jsx)

• Cover art mosaic: 2×2 grid built from the first four tracks' artwork (Artwork.jsx already resolves per-track art + fallback) instead of a generic tile
• Show track count and total duration per playlist row

Feedback & notices

• Replace inline import notices (importnote in ImportButton.jsx) with a toast component that slides above the dock and auto-dismisses — reusable for "added to playlist", sync results (see the a-Shell sync issue), and update notices
• Import progress: per-file count exists (Importing… (n)); add a thin determinate progress bar

Search (src/components/SearchView.jsx)

• When the query is empty, show something useful instead of a blank pane: recently played + most played shortcuts (again playCount/lastPlayedAt already stored)

Acceptance criteria

Each checkbox is a self-contained PR; no data-model changes required for any of them.