Add cursor-tracking card glare and accent-linked background blobs

- Subtle radial glare follows cursor over card/template-card elements
  using a single document-level mousemove listener (event delegation)
- Ambient background blob colors now derive from the selected accent
  color with hue-shifted variants
- Glare intensity kept very subtle (3.5% dark / 12% light theme)

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

server/src/wled_controller/static/js/app.js

@@ -10,6 +10,9 @@ import { Modal } from './core/modal.js';
 import { loadServerInfo, loadDisplays, configureApiKey, startConnectionMonitor, stopConnectionMonitor } from './core/api.js';
 import { t, initLocale, changeLocale } from './core/i18n.js';
 
+// Layer 1.5: visual effects
+import { initCardGlare } from './core/card-glare.js';
+
 // Layer 2: ui
 import {
     toggleHint, lockBody, unlockBody, closeLightbox,
@@ -528,6 +531,9 @@ document.addEventListener('DOMContentLoaded', async () => {
     // Show content now that translations are loaded and tabs are set
     document.body.style.visibility = 'visible';
 
+    // Initialize card glare effect
+    initCardGlare();
+
     // Set CSS variable for sticky header height (header now includes tab bar)
     const headerEl = document.querySelector('header');
     if (headerEl) {