feat: implement UsersModule with service, controller, and DTOs

Added UsersModule to manage user-related operations. Includes UsersService for CRUD operations, consent updates, and 2FA handling. Implemented UsersController with endpoints for public profiles, account management, and admin user listing. Integrated with CryptoService and database schemas.

backend/src/users/dto/update-user.dto.ts

@@ -0,0 +1,8 @@
+import { IsOptional, IsString, MaxLength } from "class-validator";
+
+export class UpdateUserDto {
+	@IsOptional()
+	@IsString()
+	@MaxLength(32)
+	displayName?: string;
+}