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.

backend/src/user-products/dto/upsert-user-product.dto.ts

@@ -0,0 +1,22 @@
+import { IsInt, IsString, IsOptional, IsBoolean } from 'class-validator';
+
+export class UpsertUserProductDto {
+  @IsInt()
+  productId: number;
+
+  @IsOptional()
+  @IsString()
+  note?: string;
+
+  @IsOptional()
+  @IsString()
+  preferredBrand?: string;
+
+  @IsOptional()
+  @IsString()
+  preferredStore?: string;
+
+  @IsOptional()
+  @IsBoolean()
+  isPrivate?: boolean;
+}