feat(web): add /requests user-facing request history

Renders the caller's Lidarr requests as rows with kind pill,
StatusPill, and per-status actions: Cancel on pending (which
calls cancelRequest then invalidates qk.myRequests()), Listen
link on completed (deepest match wins: track > album > artist),
admin notes on rejected. Empty state uses the voice-rule
"Nothing requested yet." copy. Shell nav gains /requests
between /discover and /playlists, visible to all authed users
since the view is per-user.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/src/lib/components/Shell.svelte

@@ -26,6 +26,7 @@
     { href: '/library/liked', label: 'Liked' },
     { href: '/search',        label: 'Search' },
     { href: '/discover',      label: 'Discover' },
+    { href: '/requests',      label: 'Requests' },
     { href: '/playlists',     label: 'Playlists' },
     { href: '/settings',      label: 'Settings' }
   ];

web/src/lib/components/Shell.test.ts

@@ -28,11 +28,12 @@ describe('Shell', () => {
     expect(screen.getByText('alice')).toBeInTheDocument();
   });
 
-  test('renders nav items including Discover between Search and Playlists', () => {
+  test('renders nav items including Discover and Requests between Search and Playlists', () => {
     render(Shell);
     expect(screen.getByRole('link', { name: 'Library' })).toHaveAttribute('href', '/');
     expect(screen.getByRole('link', { name: 'Search' })).toHaveAttribute('href', '/search');
     expect(screen.getByRole('link', { name: 'Discover' })).toHaveAttribute('href', '/discover');
+    expect(screen.getByRole('link', { name: 'Requests' })).toHaveAttribute('href', '/requests');
     expect(screen.getByRole('link', { name: 'Playlists' })).toHaveAttribute('href', '/playlists');
   });