feat(01-02): design token system, i18n framework, and theme provider setup

- OKLCH design tokens with yellow #ffed00 primary and dark gray-blue dark mode
- next-intl cookie-based locale with DE/EN message files
- next-themes provider with system/light/dark support
- Sidebar and header layout dimension tokens
- Root layout with ThemeProvider and NextIntlClientProvider wrappers

apps/web/package.json

@@ -10,15 +10,18 @@
   },
   "dependencies": {
     "next": "^15.3.0",
+    "next-intl": "^4.13.0",
+    "next-themes": "^0.4.6",
     "react": "^19.0.0",
-    "react-dom": "^19.0.0"
+    "react-dom": "^19.0.0",
+    "zustand": "^5.0.14"
   },
   "devDependencies": {
-    "tailwindcss": "^4.0.0",
     "@tailwindcss/postcss": "^4.0.0",
-    "postcss": "^8.0.0",
-    "typescript": "^5.5.0",
     "@types/react": "^19.0.0",
-    "@types/react-dom": "^19.0.0"
+    "@types/react-dom": "^19.0.0",
+    "postcss": "^8.0.0",
+    "tailwindcss": "^4.0.0",
+    "typescript": "^5.5.0"
   }
 }