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' }
   ];