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/base.css

@@ -6,9 +6,25 @@
 
 :root {
     --primary-color: #4CAF50;
+    --primary-hover: #5cb860;
     --danger-color: #f44336;
     --warning-color: #ff9800;
     --info-color: #2196F3;
+    --font-mono: 'Cascadia Code', 'Fira Code', 'JetBrains Mono', 'SF Mono', 'Consolas', 'Liberation Mono', monospace;
+}
+
+/* ── SVG icon base ── */
+.icon {
+    display: inline-block;
+    width: 1em;
+    height: 1em;
+    vertical-align: -0.125em;
+    fill: none;
+    stroke: currentColor;
+    stroke-width: 2;
+    stroke-linecap: round;
+    stroke-linejoin: round;
+    flex-shrink: 0;
 }
 
 /* Dark theme (default) */