What problem does this address?

Add comprehensive E2E tests covering all upload scenarios, format conversions, and error conditions.

Acceptance Criteria:

• Tests for basic image upload with compression
• Tests for sub-size generation
• Tests for uploading multiple images
• Tests for error scenarios and fallbacks
• Tests for different browser capabilities
• Performance regression tests - set and record benchmark and add to existing performance dashboard
• Test all supported mime types, format conversion
• Test special handling for transparencies, rotated images, oversized images