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>

README.md

@@ -1,5 +1,5 @@
 <div align="center">
-  <img src="public/logo.png" alt="Psysonic Logo" width="200"/>
+  <img src="public/logo-psysonic.png" alt="Psysonic Logo" width="200"/>
   <h1>Psysonic</h1>
   <p><strong>A modern, gorgeous, and blazing fast desktop client for Subsonic API compatible music servers (Navidrome, Gonic, etc.).</strong></p>