feat(desktop): Several style improvements, UX optimizations etc

[aaroniker]

UI/UX Polish:

• Added cycling text animation with staggered character rotation for the model variant button
• New ScrollFade and ScrollReveal components for fade effects on scrollable content
• Updated dropdown menu and select animations (scaleY instead of scale, smoother timing)
• Added transitions to buttons, popovers, dropdowns etc
• Increased popover/select gutters (8px → 12px/16px)
  Styling tweaks:
• Button padding standardized to 4px 8px
• Fixed mask-image fade out for scrolling lists
• List gap reduced (12px → 8px), added ScrollFade
• Message nav layout updates (gaps, padding, hover states)
• Dialog content padding-bottom added
• Select item checkmark updated to use check icon with strong color
  Fixes:
• Paste handling improved: validates file types, shows toast for unsupported files
• Project avatar component extracted with favicon validation
• Session review buttons shortened ("Collapse all" → "Collapse")

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found