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/static/css/modal.css

@@ -477,8 +477,13 @@
 .form-collapse > summary::-webkit-details-marker { display: none; }
 
 .form-collapse > summary::before {
-    content: '▶';
-    font-size: 0.6rem;
+    content: '';
+    display: inline-block;
+    width: 0;
+    height: 0;
+    border-left: 0.35em solid currentColor;
+    border-top: 0.25em solid transparent;
+    border-bottom: 0.25em solid transparent;
     opacity: 0.6;
     transition: transform 0.2s cubic-bezier(0.4, 0, 0.2, 1);
     flex-shrink: 0;