feat: add MailModule to app imports

backend/src/app.module.ts

@@ -4,6 +4,7 @@ import { AppController } from "./app.controller";
 import { AppService } from "./app.service";
 import { CryptoModule } from "./crypto/crypto.module";
 import { DatabaseModule } from "./database/database.module";
+import { MailModule } from "./mail/mail.module";
 import { S3Module } from "./s3/s3.module";
 
 @Module({
@@ -11,6 +12,7 @@ import { S3Module } from "./s3/s3.module";
 		DatabaseModule,
 		CryptoModule,
 		S3Module,
+		MailModule,
 		ConfigModule.forRoot({
 			isGlobal: true,
 		}),