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/streams.css

@@ -13,6 +13,7 @@
     border: 1px solid var(--border-color);
     border-radius: 8px;
     padding: 16px;
+    overflow: hidden;
     transition: box-shadow 0.2s ease, transform 0.2s ease;
     display: flex;
     flex-direction: column;