feat(whats-new): remote release notes with dev workspace mode (#1058)

* feat(whats-new): remote release notes with dev workspace mode

Add WHATS_NEW.md, CI whats-new.md asset upload, and client fetch/cache
with embedded fallbacks. Dev and -dev builds read the full file from the
repo for debugging; RC/stable download the release asset on first use.

* fix(whats-new): render ## headings and add changelog tab

Parse h2 sections in release-notes markdown; load changelog alongside
highlights and let users switch views on the What's New page.

* fix(whats-new): prefetch on startup and fix CI typecheck prebuild

Prefetch whats-new asset when the shell loads on RC/stable builds.
Run prebuild:release-notes before tsc and coverage jobs so the
gitignored generated bundle exists in CI.

* docs: CHANGELOG and credits for What's New remote notes (PR #1058)

* fix(whats-new): always slice embedded release notes to current line

Drop full CHANGELOG embed for -dev bundles; tauri:dev still reads live
markdown from the repo. Ignore all of src/generated/ in git.

* fix(whats-new): fetch release asset via Rust to bypass CORS

Route whats-new.md download through fetch_url_bytes; rename the
technical tab label; add fetch unit tests (PR #1058 review).

WHATS_NEW.md

@@ -0,0 +1,51 @@
+# What's New
+
+User-facing release highlights for the in-app **What's New** screen. Maintainers refresh the
+current line before promoting to `next` / `release`. Technical details and PR credits stay in
+`CHANGELOG.md`.
+
+## [1.48.0]
+
+## Highlights
+
+### Theme Store
+
+- Browse and install community themes from **Settings → Themes** — search, dark/light filter, and full-size previews.
+- Six palettes ship with the app; everything else installs on demand and works offline after the first download.
+- Import a theme from a local `.zip` when you have a package from a friend or your own design.
+- The sidebar nudges you when an installed theme has an update; one-click update from the theme card.
+
+### Offline listening
+
+- Starred tracks and pinned albums stay on disk under one **media** folder — browse them in **Offline Library**.
+- Favorites can sync automatically; pinned albums and playlists refresh when the library index updates.
+- When the server is unreachable, browse and detail pages show what you already have locally instead of empty errors.
+
+### Fullscreen player
+
+- Rebuilt for much lower CPU and memory use: a calm, sharp fullscreen view with album art, waveform seekbar, up-next queue, synced lyrics, ratings, and a clock.
+
+### Queue — Timeline mode
+
+- A third queue layout keeps the current track in the middle with history above and up next below — great for long listening sessions. Cycle the header control or pick it in **Settings → Personalisation → Queue display**.
+
+### Sidebar
+
+- Optional **Settings → Sidebar** toggle pins **Now Playing** to the top of the sidebar.
+
+### Startup
+
+- A themed loading splash appears while the app starts — colours follow your active theme, including community palettes.
+
+### Settings → Servers
+
+- Server cards are easier to scan: software version on the card, compact actions, and a green **AudioMuse-AI** badge on Navidrome 0.62+ when the plugin is detected.
+
+## Improved
+
+- Audio decoding runs on **Symphonia 0.6** for current and future codec fixes.
+- **Settings → About** shows a clearer open-source licenses panel.
+
+## Fixed
+
+- Smoother playback and library behaviour across offline mode, theme switching, and server reconnect — see `CHANGELOG.md` for the full list.