music: /music route + nav dock item (Spotify-style page, v1)

A full-page music browser reusing the app-wide player + dock. Sidebar lists
libraries (1st level of ~/Music); main is a card-grid folder browse with rich
pages: albums show a header + tracklist, and artist folders render their album
cards grouped into discography sections (Studio Albums / Live / Compilation / …)
using /music/discography. Cards have hover-play; everything feeds useMusicPlayer.
Adds a green Music dock item (/music) to the default dock.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/apps/officer-web/App.tsx

@@ -40,6 +40,7 @@ export function App() {
             <Route path="/chat/:sessionId" element={<Dashboard.SessionListPage />} />
             <Route path="/plans" element={<Dashboard.Plans />} />
             <Route path="/files" element={<Dashboard.FilesScreen />} />
+            <Route path="/music" element={<Dashboard.MusicScreen />} />
 
             <Route path="/code-editor" element={<Dashboard.CodeEditor />} />
             <Route path="/skills" element={<Dashboard.Skills />} />