Standardize all icons to uniform inline SVG format

Replace emojis throughout the codebase with inline SVG icons using
the Icons utility. Remove decorative icons where text labels already
describe the content. Add classification dot CSS for risk indicators.

- Extend Icons utility with comprehensive SVG icon set
- Update navigation, header stats, and action buttons
- Update playback controls and volume icons
- Remove decorative device type and panel header emojis
- Clean up notifications and alert messages
- Add CSS for classification status dots

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/js/core/audio.js

@@ -211,7 +211,7 @@ function isMuted() {
 function updateMuteButton() {
     const btn = document.getElementById('muteBtn');
     if (btn) {
-        btn.innerHTML = audioMuted ? '🔇 UNMUTE' : '🔊 MUTE';
+        btn.innerHTML = audioMuted ? Icons.volumeOff('icon--sm') + ' UNMUTE' : Icons.volumeOn('icon--sm') + ' MUTE';
         btn.classList.toggle('muted', audioMuted);
     }
 }
@@ -226,7 +226,7 @@ function requestNotificationPermission() {
         Notification.requestPermission().then(permission => {
             notificationsEnabled = permission === 'granted';
             if (notificationsEnabled && typeof showInfo === 'function') {
-                showInfo('🔔 Desktop notifications enabled');
+                showInfo('Desktop notifications enabled');
             }
         });
     }