fix(upload): improve bulk upload inline validation and update tests

Description:

Implemented and updated validation behavior for bulk image uploads along with related test case improvements.

Changes made:

• Split and updated related test cases for better maintainability.
• Added test coverage for bulk upload validation flow.
• Added live inline validation for bulk upload title and description fields.
• Validation behavior now matches the single upload experience.
• Error messages appear only after user interaction.
• Title validation:
  • Shows error when input is less than 8 characters.
  • Removes error immediately after valid input.
• Description validation:
  • Shows error when input is less than 32 characters.
  • Removes error immediately after valid input.
• Added per-file validation handling for each bulk uploaded item.
• Prevented invalid bulk uploads from being submitted.
• Fixed async cleanup issue in MediaGridItem to prevent unhandled Vitest errors.
• Added proper cleanup handling to avoid state updates after component unmount.
• Verified all tests, lint checks, and build are passing successfully.

Type of Change:

• Bug Fix
  • Testing
  • Feature Development
  • Documentation

Testing:

• Tested on desktop
  • Tested on mobile
  • Tested in different browsers

Screenshots (if applicable):

Added screenshots for:

• Bulk upload validation errors

• Valid state after correct input

• Updated upload flow UI

  

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Link to code walkthrough:

Added walkthrough/demo recording explaining the implemented changes and test updates.

Checklist:

• Code follows project style guidelines
  • Self-review completed
  • No console errors
  • TypeScript types are correct