Add UI Customization Panel with full color theming

- New "Interfaccia" panel with color picker (HSV + hex/RGB/alpha + 30 presets)
- Profile background customization tab
- Accent color propagates via CSS variables to: card headers/tabs,
  context menus, Button dark/primary/gray variants, InfoStand panels,
  toolbar, room tools, purse, .btn-primary/.btn-dark CSS classes
- All elements use var(--name, fallback) for zero visual change when default
- Settings persisted in localStorage
- Added react-colorful dependency
- Added ui-config.json with header images config keys

src/css/purse/PurseView.css

@@ -22,7 +22,7 @@
 			pointer-events: all;
         }
         .borderhccontent{
-            background-color: #212131;
+            background-color: var(--ui-dark-bg, #212131);
             border-radius: 0.5rem!important;
             border: 2px solid #383853;
             height: calc(100% - 3px);
@@ -46,7 +46,7 @@
     }
 
     .nitro-purse-seasonal-currency {
-        background-color: #212131;
+        background-color: var(--ui-dark-bg, #212131);
 		background: linear-gradient(to right, #5f5f8d, transparent);
 		height: 30px;
         margin-bottom: 4px;