feat(i18n): implement internationalization support for website

Add i18next with Chinese and English language support across all website sections. Convert hardcoded strings to translation keys in about, cases, services, team, footer, hero, and navbar components. Update document title and meta description to use translated values. Add language toggle in navbar. Remove contact section and unused UI components (button, card, input, textarea).

BREAKING CHANGE: Site content now requires translation files to render properly. Removed @radix-ui/react-slot and class-variance-authority dependencies as contact form UI components were deleted.

package.json

@@ -9,13 +9,14 @@
     "preview": "vite preview"
   },
   "dependencies": {
-    "@radix-ui/react-slot": "^1.2.4",
-    "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "geist": "^1.7.0",
+    "i18next": "^26.0.8",
+    "i18next-browser-languagedetector": "^8.2.1",
     "lucide-react": "^0.503.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
+    "react-i18next": "^17.0.6",
     "tailwind-merge": "^3.2.0"
   },
   "devDependencies": {