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/components/OfflineBanner.tsx

@@ -1,18 +1,34 @@
 import React from 'react';
-import { WifiOff, RefreshCw } from 'lucide-react';
+import { WifiOff, RefreshCw, Settings } from 'lucide-react';
 import { useTranslation } from 'react-i18next';
+import { useNavigate } from 'react-router-dom';
 
 interface Props {
   onRetry: () => void;
   isChecking: boolean;
+  showSettingsLink?: boolean;
+  serverName?: string;
 }
 
-export default function OfflineBanner({ onRetry, isChecking }: Props) {
+export default function OfflineBanner({ onRetry, isChecking, showSettingsLink, serverName }: Props) {
   const { t } = useTranslation();
+  const navigate = useNavigate();
+  const message = showSettingsLink
+    ? t('connection.offlineNoCacheBanner', { server: serverName })
+    : t('connection.offlineModeBanner');
   return (
     <div className="offline-banner">
       <WifiOff size={14} />
-      <span>{t('connection.offlineModeBanner')}</span>
+      <span>{message}</span>
+      {showSettingsLink && (
+        <button
+          className="offline-banner-retry"
+          onClick={() => navigate('/settings', { state: { tab: 'server' } })}
+        >
+          <Settings size={12} />
+          {t('connection.serverSettings')}
+        </button>
+      )}
       <button
         className="offline-banner-retry"
         onClick={onRetry}