fix(offline): replace blocking overlay with slim banner; add server settings link (#170)

When offline with no cached content, the full-screen OfflineOverlay blocked
all navigation including Settings, making it impossible to fix a broken
server config. Replace it with the same slim banner used in offline-cache mode.

- OfflineBanner now handles both cases: cache (existing) and no-cache (new)
- No-cache banner shows server name and a direct link to Settings → Server tab
- OfflineOverlay component is no longer used (import removed from App.tsx)
- All 8 locales: added offlineNoCacheBanner and serverSettings keys

Fixes #170

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/locales/en.ts

@@ -338,6 +338,7 @@ export const enTranslation = {
     offlineTitle: 'No server connection',
     offlineSubtitle: 'Cannot reach {{server}}. Check your network or server.',
     offlineModeBanner: 'Offline Mode — playing from local cache',
+    offlineNoCacheBanner: 'No server connection — cannot reach {{server}}',
     offlineLibraryTitle: 'Offline Library',
     offlineLibraryEmpty: 'No albums cached yet. Go online, open an album and click "Make available offline".',
     offlineAlbumCount: '{{n}} album',
@@ -347,6 +348,7 @@ export const enTranslation = {
     offlineFilterPlaylists: 'Playlists',
     offlineFilterArtists: 'Discographies',
     retry: 'Retry',
+    serverSettings: 'Server Settings',
     lastfmConnected: 'Last.fm connected as @{{user}}',
     lastfmSessionInvalid: 'Session invalid — click to re-connect',
   },