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/nl.ts

@@ -336,6 +336,7 @@ export const nlTranslation = {
     offlineTitle: 'Geen serververbinding',
     offlineSubtitle: 'Kan {{server}} niet bereiken. Controleer je netwerk of server.',
     offlineModeBanner: 'Offline modus — afspelen vanuit lokale cache',
+    offlineNoCacheBanner: 'Geen serververbinding — {{server}} niet bereikbaar',
     offlineLibraryTitle: 'Offline bibliotheek',
     offlineLibraryEmpty: 'Nog geen albums gecached. Ga online, open een album en klik op "Offline beschikbaar maken".',
     offlineAlbumCount: '{{n}} album',
@@ -345,6 +346,7 @@ export const nlTranslation = {
     offlineFilterPlaylists: 'Afspeellijsten',
     offlineFilterArtists: 'Discografieën',
     retry: 'Opnieuw proberen',
+    serverSettings: 'Serverinstellingen',
     lastfmConnected: 'Last.fm verbonden als @{{user}}',
     lastfmSessionInvalid: 'Sessie ongeldig — klik om opnieuw te verbinden',
   },