🎨 Palette: Enhance Accessibility for Form Labels and Drop Zone

[Nawayisus]

💡 What: Added for attributes to form labels, made the custom file drop zone keyboard accessible (tabindex, role, and keydown events for Enter/Space), and dynamically updated aria-valuenow on the progress bar. Also recorded a custom drop zone accessibility learning in .Jules/palette.md.
🎯 Why: To improve the application's overall accessibility for screen readers and keyboard-only users, ensuring that key interactive elements like the file drop zone and form fields are properly described and operable.
📸 Before/After: Visuals verified via temporary Playwright scripts (focus states and interactions).
♿ Accessibility: Improved form labeling, custom component (drop zone) keyboard navigation and semantic roles, and dynamic progress tracking values.

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PR created automatically by Jules for task 13396316843247012786 started by @Nawayisus

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