feat(auth): implement user authentication with JWT and NextAuth

- Added user registration and login functionality with JWT authentication.
- Created auth controller, service, and module in the backend.
- Implemented user model and user products management.
- Integrated NextAuth for session management on the frontend.
- Added middleware for protecting routes and handling public access.
- Updated frontend API routes to include authorization headers.
- Enhanced recipe and user product models to support ownership and visibility.
- Created registration and login pages in the frontend.
- Added necessary types for NextAuth session management.

frontend/app/api/admin/merge-preview-proxy/route.ts

@@ -1,9 +1,11 @@
 import { NextRequest, NextResponse } from 'next/server';
+import { getAuthHeaders } from '../../../../lib/auth-headers';
 
 const API_BASE =
   process.env.NEXT_PUBLIC_API_URL_INTERNAL || 'http://recipe-api:8080';
 
 export async function GET(request: NextRequest) {
+  const authHeaders = await getAuthHeaders();
   const sourceProductId = request.nextUrl.searchParams.get('sourceProductId');
   const targetProductId = request.nextUrl.searchParams.get('targetProductId');
 
@@ -11,6 +13,7 @@ export async function GET(request: NextRequest) {
     `${API_BASE}/api/products/merge-preview?sourceProductId=${sourceProductId}&targetProductId=${targetProductId}`,
     {
       method: 'GET',
+      headers: { ...authHeaders },
       cache: 'no-store',
     },
   );