fix: add image upload size limits for hackathon (#63)

- useUploadFile: add 5MB limit + image type validation for team
  logo/banner uploads (was unrestricted)
- useUploadAvatar: tighten limit from 5MB to 2MB per issue request
- Submit page: switch from useUploadFile to useUploadSubmission
  which has proper 50MB limit + broader file type support

Size limits:
  - Profile avatar: 2MB (JPEG, PNG, WebP, GIF)
  - Team logo/banner: 5MB (JPEG, PNG, WebP, GIF)
  - Team files: 20MB (images + PDF)
  - Submissions: 50MB (images, PDF, ZIP, video)

Closes #63

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/hackathon/src/app/teams/[teamId]/submit/page.tsx

@@ -9,7 +9,7 @@ import {
   useSubmitProject,
   useTeamById,
   useTeamSubmission,
-  useUploadFile,
+  useUploadSubmission,
   useAuthStore,
 } from '@imphnen-frontend-service/service';
 import { zodResolver } from '@hookform/resolvers/zod';
@@ -67,7 +67,7 @@ const SubmitProjectPage: FC = (): ReactElement => {
   const { data: submissionData } = useTeamSubmission(teamId || '', !!teamId);
   const { mutateAsync: submitProject, isPending: isSubmitting } =
     useSubmitProject(teamId || '');
-  const { mutateAsync: uploadFile, isPending: isUploading } = useUploadFile();
+  const { mutateAsync: uploadFile, isPending: isUploading } = useUploadSubmission();
 
   const team = teamData?.data;
   const currentUserId = session?.user?.id;