feat: UI color theming system with live preview, presets and server sync

- RGBA color picker with live preview (debounce 50ms)
- 30 preset colors + 12 theme presets (Ocean, Forest, Sunset, Royal, etc.)
- Header image selection from configurable image library
- Export/Import theme as JSON via clipboard
- CSS variable theming across all UI elements: NitroCard headers/tabs,
  context menus, buttons (primary/dark/gray), InfoStand, toolbar,
  room tools, purse, progress bars, sliders
- All elements use var(--name, fallback) for zero visual change when default
- Smooth 0.3s CSS transitions on theme change
- Server-side persistence via WebSocket (packets 10047/10048)
- Integrated Color/Image tabs into BackgroundsView panel
- All strings use LocalizeText() for i18n support
- Settings persisted in localStorage + server sync with 1s debounce
- Added react-colorful dependency

src/common/layout/LayoutProgressBar.tsx

@@ -14,7 +14,7 @@ export const LayoutProgressBar: FC<LayoutProgressBarProps> = props =>
 
     const getClassNames = useMemo(() =>
     {
-        const newClassNames: string[] = [ 'border border-[solid] border-[#fff] p-[2px] h-[20px] rounded-[.25rem] overflow-hidden bg-[#1E7295]        ', 'text-white' ];
+        const newClassNames: string[] = [ 'border border-[solid] border-[#fff] p-[2px] h-[20px] rounded-[.25rem] overflow-hidden', 'text-white' ];
 
         if(classNames.length) newClassNames.push(...classNames);
 
@@ -22,7 +22,7 @@ export const LayoutProgressBar: FC<LayoutProgressBarProps> = props =>
     }, [ classNames ]);
 
     return (
-        <Column classNames={ getClassNames } justifyContent={ justifyContent } position={ position } { ...rest }>
+        <Column classNames={ getClassNames } justifyContent={ justifyContent } position={ position } style={ { backgroundColor: 'var(--ui-accent-color, #1E7295)' } } { ...rest }>
             { text && (text.length > 0) &&
                 <Flex center fit className="[text-shadow:0px_4px_4px_rgba(0,0,0,.25)] z-20" position="absolute">{ text }</Flex> }
             <Base className="h-full z-10 [transition:all_1s] rounded-[.125rem] bg-[repeating-linear-gradient(#2DABC2,#2DABC2_50%,#2B91A7_50%,#2B91A7_100%)]" style={ { width: (~~((((progress - 0) * (100 - 0)) / (maxProgress - 0)) + 0) + '%') } } />