Refactor API Requests

[georginikolov7]

Once BE switches to accepting multipart/form-data instead of application/json for PUT and PATCH requests, we need to refactor the FE so it sends the appropriate form data.

Task

1. Refactor apiClient; make it as generic as possible
2. Refactor all admin panel pages that have image_url field to have a file_upload field. Said field needs to be validated for file_type: ONLY .jpg, .png, .webp are accepted, file size is maximum: (WiP) MB
3. Using the new apiClient.ts send the appropriate requests

Pages to refactor:

• Sponsors
• Judges
• Past Events
• Mentors
• Meet-the-team
  (AKA all of them without Feature Switches)

Requirements:

1. PUT and PATCH on endpoints that accept image are multipart/form-data and not just json.
2. File Fields are validated as per above description