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/css/cards.css

@@ -56,6 +56,7 @@ section {
     border-radius: 8px;
     padding: 12px 20px 20px;
     position: relative;
+    overflow: hidden;
     transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
     display: flex;
     flex-direction: column;
@@ -66,6 +67,38 @@ section {
     transform: translateY(-2px);
 }
 
+/* ── Card glare effect ── */
+.card-glare::after,
+.template-card.card-glare::after {
+    content: '';
+    position: absolute;
+    inset: 0;
+    border-radius: inherit;
+    pointer-events: none;
+    opacity: 0;
+    transition: opacity 0.3s ease;
+    background: radial-gradient(
+        circle 200px at var(--glare-x, 50%) var(--glare-y, 50%),
+        rgba(255, 255, 255, 0.035) 0%,
+        transparent 70%
+    );
+    z-index: 1;
+}
+
+.card-glare::after,
+.template-card.card-glare::after {
+    opacity: 1;
+}
+
+[data-theme="light"] .card-glare::after,
+[data-theme="light"] .template-card.card-glare::after {
+    background: radial-gradient(
+        circle 200px at var(--glare-x, 50%) var(--glare-y, 50%),
+        rgba(255, 255, 255, 0.12) 0%,
+        transparent 70%
+    );
+}
+
 /* ── Card entrance animation ── */
 @keyframes cardEnter {
     from { opacity: 0; transform: translateY(12px); }