feat: add shimmer animation for title generation

[devin-ai-integration]

Summary

Adds a shimmer loading animation to the title input field while the AI is generating a title after summary completion. When the title task is in "generating" state, the input field is replaced with an animated shimmer placeholder to provide visual feedback.

Changes:

• Track title generation status using useAITaskTask hook in TitleInput component
• Render shimmer placeholder when isTitleGenerating is true
• Add animate-shimmer keyframes to Tailwind config

Closes #2628

Review & Testing Checklist for Human

• Verify shimmer animation visually: Run the app, complete a recording session, and confirm the shimmer appears while title is being generated and looks smooth
• Check shimmer dimensions: The shimmer is hardcoded to w-48 (192px) - verify this looks appropriate for typical title lengths and doesn't cause layout shift
• Test the full flow: Stop recording → summary generates → title shimmer appears → title populates correctly

Test Plan

1. Start a recording session with some speech
2. Stop the recording
3. Observe the summary being generated
4. When summary completes, verify the title field shows a shimmer animation
5. Confirm the generated title replaces the shimmer correctly

Notes

• The shimmer animation uses a gradient background that animates from right to left
• Animation timing is 1.5s ease-in-out infinite
• This PR was not tested locally with the desktop app running

Link to Devin run: https://app.devin.ai/sessions/a8111e0951444951b0e961da717a4419
Requested by: john@hyprnote.com (@ComputelessComputer)

[devin-ai-integration]

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