Add card color system with wrapCard helper and reset support

Introduce localStorage-backed card color assignment for all card types
with a reusable wrapCard() helper that provides consistent card shell
structure (top actions, bottom actions with color picker). Move color
picker from top-right to bottom-right action bar. Add color reset
button to clear card color back to default.

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

server/src/wled_controller/static/locales/en.json

@@ -5,6 +5,7 @@
   "theme.toggle": "Toggle theme",
   "accent.title": "Accent color",
   "accent.custom": "Custom",
+  "accent.reset": "Reset",
   "locale.change": "Change language",
   "auth.login": "Login",
   "auth.logout": "Logout",