chore(deps): update dependencies and remove unused files

Updated several dependencies including:
- @aws-sdk/client-s3 from 3.965.0 to 3.975.0
- @aws-sdk/client-ses from 3.965.0 to 3.975.0
- @aws-sdk/client-sqs from 3.965.0 to 3.975.0
- dotenv from ^16.6.1 to ^16.5.0
- form-data from ^4.0.2 to ^4.0.5
- typescript from 5.9.3 to 5.8.3

Removed unused files:
- backend/.yarn/releases/yarn-4.9.1.cjs
- backend/package-lock.json

backend/types/form-data.d.ts

@@ -0,0 +1,12 @@
+// Form-data type declarations
+declare module 'form-data' {
+  import { Readable } from 'stream';
+
+  class FormData {
+    append(name: string, value: any, options?: any): void;
+    getHeaders(userHeaders?: any): any;
+    submit(params: any, callback?: any): any;
+  }
+
+  export = FormData;
+}