fix: Update Tailwind CSS and Better Auth imports for frontend build

- Update Tailwind CSS v4 PostCSS configuration
- Fix Better Auth React imports (better-auth/react)
- Update all page components to use Better Auth useSession
- Add @tailwindcss/postcss to dependencies
- Remove SessionProvider from layout (Better Auth handles sessions)
- Fix globals.css for Tailwind v4 compatibility
- Update page components with correct session state checking

This addresses build failures related to:
- Tailwind CSS v4 PostCSS plugin compatibility
- Better Auth React client import paths
- NextAuth v5 to Better Auth migration

frontend/package.json

@@ -8,30 +8,29 @@
     "lint": "next lint"
   },
   "dependencies": {
-    "next": "16.1.6",
-    "better-auth": "^1.4.18",
-    "react": "^19.2.4",
-    "react-dom": "^19.2.4",
-    "recharts": "^3.7.0",
-    "lucide-react": "^0.574.0",
-    "date-fns": "^4.1.0",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",
     "@radix-ui/react-slot": "^1.2.4",
     "@radix-ui/react-tabs": "^1.1.13",
     "@radix-ui/react-toast": "^1.2.15",
+    "better-auth": "^1.4.18",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "date-fns": "^4.1.0",
+    "lucide-react": "^0.574.0",
+    "next": "16.1.6",
+    "react": "^19.2.4",
+    "react-dom": "^19.2.4",
+    "recharts": "^3.7.0",
     "tailwind-merge": "^3.5.0"
   },
   "devDependencies": {
     "@types/node": "^25.3.0",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
-    "typescript": "^5.9.3",
-    "tailwindcss": "^4.2.0",
-    "postcss": "^8.5.6",
     "autoprefixer": "^10.4.24",
-    "@tailwindcss/postcss": "^4.0.0"
+    "postcss": "^8.5.6",
+    "tailwindcss": "^3.4.17",
+    "typescript": "^5.9.3"
   }
 }