feat: integrate HeroUI component library

Implemented HeroUI migration plan with the following changes:

Stage 0: Environment Setup
- Installed @heroui/react@2.8.7, @heroui/theme@2.4.26, framer-motion@12.29.2
- Configured Tailwind with HeroUI plugin
- Added HeroUI content paths to Tailwind config

Stage 1: Provider Architecture
- Created Providers.tsx wrapper combining HeroUIProvider and AppProvider
- Updated app/layout.tsx to use new Providers component
- Preserved all AppContext functionality (theme, language, translations)

Stage 2: Component Migrations
- TabNavigation: Migrated to HeroUI Tabs with keyboard navigation support
- TopBar: Migrated buttons to HeroUI Button components
- LanguageSwitch: Migrated to HeroUI Dropdown for better UX
- ThemeSwitch: Migrated to HeroUI Button (isIconOnly variant)
- MintSwapPanel: Migrated to HeroUI Tabs and Button components

Benefits:
- Enhanced accessibility with ARIA attributes and keyboard navigation
- Smooth animations and transitions via Framer Motion
- Consistent component API across the application
- Maintained all existing design tokens and color system
- Preserved dark mode functionality

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

components/LanguageSwitch.tsx

@@ -1,22 +1,45 @@
-"use client";
-
-import { useApp } from "@/contexts/AppContext";
-
-export default function LanguageSwitch() {
-  const { language, setLanguage } = useApp();
-
-  const toggleLanguage = () => {
-    setLanguage(language === "zh" ? "en" : "zh");
-  };
-
-  return (
-    <button
-      onClick={toggleLanguage}
-      className="bg-bg-surface dark:bg-gray-800 rounded-lg border border-border-normal dark:border-gray-700 px-3 py-2 flex items-center justify-center h-10 hover:bg-gray-50 dark:hover:bg-gray-700 transition-colors"
-    >
-      <span className="text-sm font-medium text-text-primary dark:text-white">
-        {language === "zh" ? "中" : "EN"}
-      </span>
-    </button>
-  );
-}
+"use client";
+
+import { useApp } from "@/contexts/AppContext";
+import { Dropdown, DropdownTrigger, DropdownMenu, DropdownItem, Button } from "@heroui/react";
+
+export default function LanguageSwitch() {
+  const { language, setLanguage } = useApp();
+
+  const languages = [
+    { key: "zh", label: "中文" },
+    { key: "en", label: "English" },
+  ];
+
+  const handleSelectionChange = (key: React.Key) => {
+    setLanguage(key as "zh" | "en");
+  };
+
+  return (
+    <Dropdown>
+      <DropdownTrigger>
+        <Button
+          variant="bordered"
+          className="bg-bg-surface dark:bg-gray-800 border-border-normal dark:border-gray-700 min-w-10 h-10 px-3 rounded-lg"
+        >
+          <span className="text-sm font-medium text-text-primary dark:text-white">
+            {language === "zh" ? "中" : "EN"}
+          </span>
+        </Button>
+      </DropdownTrigger>
+      <DropdownMenu
+        aria-label="Language selection"
+        selectedKeys={new Set([language])}
+        selectionMode="single"
+        onSelectionChange={(keys) => {
+          const key = Array.from(keys)[0];
+          if (key) handleSelectionChange(key);
+        }}
+      >
+        {languages.map((lang) => (
+          <DropdownItem key={lang.key}>{lang.label}</DropdownItem>
+        ))}
+      </DropdownMenu>
+    </Dropdown>
+  );
+}