feat(dto): enforce field length constraints across DTOs

Add `@MaxLength` validations to limit string field lengths in multiple DTOs, ensuring consistent data validation and integrity. Integrate `CreateApiKeyDto` in the API keys controller for improved type safety.

backend/src/api-keys/dto/create-api-key.dto.ts

@@ -0,0 +1,12 @@
+import { IsDateString, IsNotEmpty, IsOptional, IsString, MaxLength } from "class-validator";
+
+export class CreateApiKeyDto {
+	@IsString()
+	@IsNotEmpty()
+	@MaxLength(128)
+	name!: string;
+
+	@IsOptional()
+	@IsDateString()
+	expiresAt?: string;
+}