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-tauri/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "psysonic"
-version = "1.4.5"
+version = "1.5.0"
 description = "Psysonic Desktop Music Player"
 authors = []
 license = ""
@@ -33,3 +33,5 @@ serde_json = "1"
 rodio = { version = "0.19", default-features = false, features = ["symphonia-all"] }
 reqwest = { version = "0.12", features = ["stream"] }
 tokio = { version = "1", features = ["rt", "time"] }
+biquad = "0.4"
+tauri-plugin-window-state = "2.4.1"