Develop (#55)

feat: optimize dashboard/search UX and simplify extension architecture

Redesign Dashboard with compact tool grid and recently used tools
Improve TopBar search UX with Cmd/Ctrl+K shortcut and better history navigation
Reorganize project structure into src/
Migrate i18n from react-i18next to chrome.i18n
Remove runtime language switch and settings page
Remove HTML/Markdown conversion tools
Clean up unused code, dead animations, redundant comments, and imports
Improve component consistency with shadcn/ui patterns
Replace hardcoded strings/colors with i18n tokens and theme tokens
Add comprehensive project documentation and coding standards
Fix CI artifact upload workflow and multiple TypeScript/test issues

Includes various refactors, UI polish, i18n cleanup, CI improvements,
and maintenance updates across the codebase.

src/components/ui/badge.tsx

@@ -0,0 +1,32 @@
+import * as React from 'react';
+import { cva, type VariantProps } from 'class-variance-authority';
+
+import { cn } from '@/lib/utils';
+
+const badgeVariants = cva(
+  'inline-flex items-center rounded-full border px-2.5 py-0.5 text-xs font-semibold transition-colors focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2',
+  {
+    variants: {
+      variant: {
+        default: 'border-transparent bg-primary text-primary-foreground hover:bg-primary/80',
+        secondary:
+          'border-transparent bg-secondary text-secondary-foreground hover:bg-secondary/80',
+        destructive:
+          'border-transparent bg-destructive text-destructive-foreground hover:bg-destructive/80',
+        outline: 'text-foreground',
+      },
+    },
+    defaultVariants: {
+      variant: 'default',
+    },
+  },
+);
+
+export interface BadgeProps
+  extends React.HTMLAttributes<HTMLDivElement>, VariantProps<typeof badgeVariants> {}
+
+function Badge({ className, variant, ...props }: BadgeProps) {
+  return <div className={cn(badgeVariants({ variant }), className)} {...props} />;
+}
+
+export { Badge, badgeVariants };