feat(ux): add loading and disabled states for async action buttons

[Antra1705]

Summary

Added consistent disabled and loading states to all action buttons that trigger async API/fetch calls across the codebase, preventing double-submissions and race conditions.

Closes #1508

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Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor / code cleanup

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Changes Made

• ConfirmModal.tsx: Added disabled prop to block Confirm/Cancel buttons and backdrop/Escape dismissal during in-flight operations
• ProjectMetrics.tsx: Added disconnecting state to Jira Disconnect button
• GoalTracker.tsx: Added incrementingId state to manual +1 button; passed disabled={deletingId !== null} to ConfirmModal during deletion
• TodayFocusHero.tsx: Added isSaving and isClearing states to Save and Clear buttons, disabling input during flight
• StreakTracker.tsx: Fixed conditional rendering of freeze block (freeze !== null instead of !freezeLoading); added loading state to Freeze/Cancel freeze buttons
• settings/page.tsx: Added disabled={saving} to Spotlight Pin, Unpin, Move Up, Move Down buttons and search input
• RoomClient.tsx: Added deleting state to Delete Room button with "Deleting..." label

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How to Test

1. Goal Tracker: Click +1 on a manual goal — button briefly disables. Delete a goal — modal buttons disable during deletion.
2. ProjectMetrics: Click Disconnect on Jira integration — button disables and shows "Disconnecting..."
3. TodayFocusHero: Click Save — button disables and shows "Saving...". Click Clear — shows "Clearing..."
4. Settings: Search and pin/unpin/reorder repos — all buttons disable while saving
5. RoomClient: Click Delete Room — button disables and shows "Deleting..."
6. StreakTracker: Click Freeze Streak — button disables and shows "Freezing..."

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Screenshots (if UI change)

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Checklist

• Linked issue in summary
• npm run lint passes locally
• No TypeScript errors (npm run type-check)
• Self-reviewed the diff
• Added/updated tests if applicable

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Accessibility Checklist

• Proper keyboard navigation tested
• Responsive UI verified
• Accessibility labels added where needed

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Additional Notes

• 34 test failures exist on the current main branch after upstream PR fix: split Supabase client into admin and browser modules for security #2114 (Supabase client refactor). Verified via git stash that zero failures are introduced by this PR — all failures pre-exist.
• All loading states follow existing patterns in the codebase (disabled:opacity-60, disabled:cursor-not-allowed).

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