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/add-device.html

@@ -4,7 +4,7 @@
         <div class="modal-header">
             <h2 id="add-device-modal-title" data-i18n="devices.add">Add New Device</h2>
             <div class="modal-header-actions">
-                <button type="button" class="modal-header-btn" id="scan-network-btn" onclick="scanForDevices()" data-i18n-title="device.scan" title="Auto Discovery">&#x1F50D;</button>
+                <button type="button" class="modal-header-btn" id="scan-network-btn" onclick="scanForDevices()" data-i18n-title="device.scan" title="Auto Discovery"><svg class="icon" viewBox="0 0 24 24"><path d="m21 21-4.34-4.34"/><circle cx="11" cy="11" r="8"/></svg></button>
                 <button class="modal-close-btn" onclick="closeAddDeviceModal()" title="Close" data-i18n-aria-label="aria.close">&#x2715;</button>
             </div>
         </div>