Replace all emoji icons with Lucide SVGs, add accent color picker

- Replace all emoji characters across WebUI with inline Lucide SVG icons
  for cross-platform consistency (icon paths in icon-paths.js)
- Add accent color picker popover with 9 preset colors + custom picker,
  persisted to localStorage, updates all CSS custom properties
- Remove subtab separator line for cleaner look
- Color badge icons with accent color for visual pop
- Remove processing badge from target cards
- Fix hardcoded #4CAF50 in FPS labels and active badges to use CSS vars
- Replace CSS content emoji (▶) with pure CSS triangle

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

server/src/wled_controller/templates/modals/test-audio-template.html

@@ -16,7 +16,7 @@
             </div>
 
             <button type="button" id="test-audio-template-start-btn" class="btn btn-primary" onclick="startAudioTemplateTest()" style="margin-top: 8px;">
-                <span data-i18n="audio_template.test.run">🧪 Run</span>
+<svg class="icon" viewBox="0 0 24 24"><path d="M14 2v6a2 2 0 0 0 .245.96l5.51 10.08A2 2 0 0 1 18 22H6a2 2 0 0 1-1.755-2.96l5.51-10.08A2 2 0 0 0 10 8V2"/><path d="M6.453 15h11.094"/><path d="M8.5 2h7"/></svg> <span data-i18n="audio_template.test.run">Run</span>
             </button>
 
             <canvas id="audio-template-test-canvas" class="audio-test-canvas" style="display:none; margin-top: 12px;"></canvas>