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/styles/layout.css

@@ -134,6 +134,45 @@
   opacity: 1;
 }
 
+/* Now Playing nav link */
+.nav-link-nowplaying {
+  color: var(--accent);
+  background: var(--accent-dim);
+  font-weight: 600;
+}
+.nav-link-nowplaying:hover {
+  background: color-mix(in srgb, var(--accent) 20%, transparent);
+  color: var(--accent);
+}
+.nav-link-nowplaying.active {
+  background: color-mix(in srgb, var(--accent) 22%, transparent);
+  color: var(--accent);
+}
+.nav-link-nowplaying svg {
+  opacity: 1;
+}
+
+.nav-np-icon-wrap {
+  position: relative;
+  display: flex;
+  align-items: center;
+  flex-shrink: 0;
+}
+.nav-np-dot {
+  position: absolute;
+  top: -3px;
+  right: -4px;
+  width: 7px;
+  height: 7px;
+  border-radius: 50%;
+  background: var(--accent);
+  animation: np-dot-pulse 1.8s ease-in-out infinite;
+}
+@keyframes np-dot-pulse {
+  0%, 100% { opacity: 1;   transform: scale(1); }
+  50%       { opacity: 0.4; transform: scale(0.7); }
+}
+
 /* Collapsed Sidebar Styles */
 .sidebar.collapsed .sidebar-brand {
   justify-content: center;