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/streams.css

@@ -538,7 +538,6 @@
     display: flex;
     align-items: center;
     gap: 4px;
-    border-bottom: 2px solid var(--border-color);
     margin-bottom: 16px;
 }
 
@@ -551,7 +550,6 @@
     color: var(--text-secondary);
     cursor: pointer;
     border-bottom: 2px solid transparent;
-    margin-bottom: -2px;
     transition: color 0.2s ease, border-color 0.25s ease;
 }