refactor(types): eliminate all as any type assertions (30 → 0)

- Replace MouseEvent-only handlers with MouseEvent | KeyboardEvent unions in multi-select and ChatTabBar
- Define LegacyInstalledPlugin type for backward compatibility in plugin-api
- Create getTokenValue() helper for type-safe theme token access in AppearanceTab
- Define ModelConfig interface for model configuration type safety in modelProvider
- All modifications maintain exact business logic equivalence
- Build passes with zero TypeScript errors (bun run build ✅)
- LSP diagnostics clean on all modified files

dashboard/src/components/ui/multi-select.tsx

@@ -79,7 +79,7 @@ function SortableBadge({
   }
 
   // 处理删除按钮点击，阻止事件冒泡和默认行为
-  const handleRemoveClick = (e: React.MouseEvent) => {
+  const handleRemoveClick = (e: React.MouseEvent | React.KeyboardEvent) => {
     e.preventDefault()
     e.stopPropagation()
     onRemove(value)
@@ -121,7 +121,7 @@ function SortableBadge({
           onKeyDown={(e) => {
             if (e.key === 'Enter' || e.key === ' ') {
               e.preventDefault()
-              handleRemoveClick(e as any)
+              handleRemoveClick(e)
             }
           }}
         >