Add dynamic UI theme for server browser

Introduce runtime-driven UI theming for the server browser

- Expose PushUITheme() in F4TServerBrowserBridge and implement ColorToJson + PushUIThemeInternal to serialize HUD colors and invoke a JS hook.
- Call PushUITheme on UI initialization and when the browser is shown so the webview receives current HUD colors.
- Add frontend handler for "uiTheme" in app.js and a new components/theme.js that implements window.applyCoTheme to set CSS vars and tint the cursor SVG.
- Update styles.css to use RGB component CSS variables (--co-r/--co-g/--co-b and background equivalents) so colors can be overridden at runtime.
- Update index.html to include the new theme script and tweak cursor SVG stroke width; cursor asset updated as well.

This enables the plugin to synchronize the in-game HUD colors with the browser UI dynamically.

ui/views/CommonwealthOnline/browser/assets/F4MouseCursor.svg

@@ -6,6 +6,7 @@
       .st0 {
         fill: #fff;
         stroke: #000;
+        stroke-width: 3.2px;
         stroke-miterlimit: 10;
       }
     </style>