feat: 10-band EQ, connection indicator, new icon (v1.5.0)

### 10-Band Graphic Equalizer
- Full EQ in Rust audio engine via EqSource<S> biquad peak filters
- 10 built-in presets + custom preset save/delete
- EqSource::try_seek() implemented — also fixes waveform seek which broke
  silently when EQ was introduced (rodio returned SeekError::NotSupported)
- EQ state persisted in localStorage, synced to Rust on startup

### Connection Indicator
- LED in header (green/red/pulsing) with server name and LAN/WAN label
- Offline overlay with retry button when server is unreachable
- useConnectionStatus hook

### New App Icon
- New logo (logo-psysonic.png) applied across Login, Sidebar, Settings,
  README and all Tauri platform icons (Windows, macOS, Linux, Android, iOS)

### Now Playing Page
- New /now-playing route added

### Fixes
- WaveformSeek: mousemove/mouseup on window to fix drag outside canvas

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

src/components/ConnectionIndicator.tsx

@@ -0,0 +1,30 @@
+import { useTranslation } from 'react-i18next';
+import { ConnectionStatus } from '../hooks/useConnectionStatus';
+
+interface Props {
+  status: ConnectionStatus;
+  isLan: boolean;
+  serverName: string;
+}
+
+export default function ConnectionIndicator({ status, isLan, serverName }: Props) {
+  const { t } = useTranslation();
+
+  const label = isLan ? 'LAN' : t('connection.extern');
+  const title =
+    status === 'connected'
+      ? t('connection.connected')
+      : status === 'disconnected'
+      ? t('connection.disconnected')
+      : t('connection.checking');
+
+  return (
+    <div className="connection-indicator" title={title}>
+      <div className={`connection-led connection-led--${status}`} />
+      <div className="connection-meta">
+        <span className="connection-type">{label}</span>
+        <span className="connection-server">{serverName}</span>
+      </div>
+    </div>
+  );
+}