♻️ refactor(StyleContext): modernize context architecture and eliminate route transition flicker

## Breaking Changes
- Remove backward compatibility layer for old action types
- StyleContext is no longer exported, use useStyle hook instead

## Major Improvements
- **Architecture**: Replace useState with useReducer for complex state management
- **Performance**: Add debounced resize handling and batch updates via BATCH_UPDATE action
- **DX**: Export useStyle hook and styleActions for type-safe usage
- **Memory**: Use useMemo to cache context value and prevent unnecessary re-renders

## Bug Fixes
- **UI**: Eliminate padding flicker when navigating to /console/chat* and /console/playground routes
- **Logic**: Remove redundant localStorage operations and state synchronization

## Implementation Details
- Define ACTION_TYPES and ROUTE_PATTERNS constants for better maintainability
- Add comprehensive JSDoc documentation for all functions
- Extract custom hooks: useWindowResize, useRouteChange, useMobileSiderAutoHide
- Calculate shouldInnerPadding directly in PageLayout based on pathname to prevent async updates
- Integrate localStorage saving logic into SET_SIDER_COLLAPSED reducer case
- Remove SET_INNER_PADDING action as it's no longer needed

## Updated Components
- PageLayout.js: Direct padding calculation based on route
- HeaderBar.js: Use new useStyle hook and styleActions
- SiderBar.js: Remove redundant localStorage calls
- LogsTable.js: Remove unused StyleContext import
- Playground/index.js: Migrate to new API

## Performance Impact
- Reduced component re-renders through optimized context structure
- Eliminated unnecessary effect dependencies and state updates
- Improved route transition smoothness with synchronous padding calculation

web/src/components/playground/MessageContent.js

@@ -136,18 +136,10 @@ const MessageContent = ({
     !finalExtractedThinkingContent &&
     (!finalDisplayableFinalContent || finalDisplayableFinalContent.trim() === '')) {
     return (
-      <div className={`${className} flex items-center gap-2 sm:gap-4 p-4 sm:p-6 bg-gradient-to-r from-purple-50 to-indigo-50 rounded-xl sm:rounded-2xl`}>
-        <div className="w-8 h-8 sm:w-10 sm:h-10 rounded-full bg-gradient-to-br from-purple-500 to-indigo-600 flex items-center justify-center shadow-lg">
+      <div className={`${className} flex items-center gap-2 sm:gap-4 bg-gradient-to-r from-purple-50 to-indigo-50 rounded-xl sm:rounded-2xl`}>
+        <div className="w-4 h-4 rounded-full bg-gradient-to-br from-purple-500 to-indigo-600 flex items-center justify-center shadow-lg">
           <Loader2 className="animate-spin text-white" size={styleState.isMobile ? 16 : 20} />
         </div>
-        <div className="flex flex-col">
-          <Typography.Text strong className="text-gray-800 text-sm sm:text-base">
-            {t('正在思考...')}
-          </Typography.Text>
-          <Typography.Text className="text-gray-500 text-xs sm:text-sm">
-            AI 正在分析您的问题
-          </Typography.Text>
-        </div>
       </div>
     );
   }