feat(playground): enhance SSE debugging and add image paste support with i18n

- Add SSEViewer component for interactive SSE message inspection
  * Display SSE data stream with collapsible panels
  * Show parsed JSON with syntax highlighting
  * Display key information badges (content, tokens, finish reason)
  * Support copy individual or all SSE messages
  * Show error messages with detailed information

- Support Ctrl+V to paste images in chat input
  * Enable image paste in CustomInputRender component
  * Auto-detect and add pasted images to image list
  * Show toast notifications for paste results

- Add complete i18n support for 6 languages
  * Chinese (zh): Complete translations
  * English (en): Complete translations
  * Japanese (ja): Add 28 new translations
  * French (fr): Add 28 new translations
  * Russian (ru): Add 28 new translations
  * Vietnamese (vi): Add 32 new translations

- Update .gitignore to exclude data directory

web/src/components/playground/SettingsPanel.jsx

@@ -122,7 +122,7 @@ const SettingsPanel = ({
             </Typography.Text>
             {customRequestMode && (
               <Typography.Text className='text-xs text-orange-600'>
-                (已在自定义模式中忽略)
+                ({t('已在自定义模式中忽略')})
               </Typography.Text>
             )}
           </div>
@@ -154,7 +154,7 @@ const SettingsPanel = ({
             </Typography.Text>
             {customRequestMode && (
               <Typography.Text className='text-xs text-orange-600'>
-                (已在自定义模式中忽略)
+                ({t('已在自定义模式中忽略')})
               </Typography.Text>
             )}
           </div>
@@ -206,19 +206,19 @@ const SettingsPanel = ({
             <div className='flex items-center gap-2'>
               <ToggleLeft size={16} className='text-gray-500' />
               <Typography.Text strong className='text-sm'>
-                流式输出
+                {t('流式输出')}
               </Typography.Text>
               {customRequestMode && (
                 <Typography.Text className='text-xs text-orange-600'>
-                  (已在自定义模式中忽略)
+                  ({t('已在自定义模式中忽略')})
                 </Typography.Text>
               )}
             </div>
             <Switch
               checked={inputs.stream}
               onChange={(checked) => onInputChange('stream', checked)}
-              checkedText='开'
-              uncheckedText='关'
+              checkedText={t('开')}
+              uncheckedText={t('关')}
               size='small'
               disabled={customRequestMode}
             />