Fixes #26908
Fixes CAL-7077

What does this PR do?

Implements optimistic updates for availability edit screens in the companion app (iOS, Android, browser extension). This is part of a larger refactoring effort to add auto-refresh/reload after save actions.

Phase 1 - EditAvailabilityNameScreen:

• Enhanced useUpdateSchedule hook with full optimistic update support (onMutate, onSuccess, onError)
• Refactored EditAvailabilityNameScreen.tsx and EditAvailabilityNameScreen.ios.tsx to use the mutation hook instead of direct API calls
• Cache is now updated immediately on save, providing instant UI feedback
• On error, cache automatically rolls back to previous state

Phase 2 - EditAvailabilityOverrideScreen:

• Refactored EditAvailabilityOverrideScreen.tsx and EditAvailabilityOverrideScreen.ios.tsx to use useUpdateSchedule mutation hook
• Replaced direct CalComAPIService.updateSchedule calls with the mutation hook
• Removed local isSaving state in favor of isPending from the mutation hook
• Override changes now update the cache automatically via optimistic updates

Phase 3 - EditAvailabilityDayScreen:

• Refactored EditAvailabilityDayScreen.tsx and EditAvailabilityDayScreen.ios.tsx to use useUpdateSchedule mutation hook
• Replaced direct CalComAPIService.updateSchedule calls with the mutation hook
• Removed local isSaving state in favor of isPending from the mutation hook
• Day availability changes now update the cache automatically via optimistic updates

Supporting Changes (by @dhairyashiil):

• Refactored AvailabilityDetailScreen.tsx and AvailabilityDetailScreen.ios.tsx to use useScheduleById hook instead of direct API calls
• This ensures the detail screen reads from React Query cache, enabling cache updates to propagate correctly
• Added RefreshControl for pull-to-refresh support
• Replaced direct API mutations with useSetScheduleAsDefault and useDeleteSchedule hooks

Updates since last revision

Fixed stale data issue on the Working Hours page (page 2 in the edit flow):

• Refactored edit-availability-hours.tsx and edit-availability-hours.ios.tsx route files to use useScheduleById hook
• Previously, these routes used direct CalComAPIService.getScheduleById() calls with local useState, bypassing the React Query cache
• Now all 3 pages in the availability edit flow (detail → working hours → day edit) read from the same cache, ensuring updates propagate correctly

Fixed Date Overrides section not clickable when empty:

• Previously, when there were no date overrides, the section was a plain View without any press handler
• Users couldn't navigate to the edit override page to add new overrides
• Now the "No Overrides" section is wrapped in AppPressable with navigation handler and chevron icon
• Follows the same pattern as other sections (Weekly Schedule, Timezone) which are always clickable

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A - internal companion app changes only.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

Phase 1 - Edit Name/Timezone:

1. Open the companion app (iOS/Android/browser extension)
2. Navigate to Availability settings
3. Edit a schedule's name or timezone
4. Save the changes
5. Navigate back to the availability list
6. Expected: List should show updated name/timezone immediately without manual refresh

Phase 2 - Edit Overrides:

1. Navigate to a schedule's detail page
2. Add, edit, or delete a date override
3. Save the changes
4. Navigate back to the detail/list page
5. Expected: Changes should reflect immediately without manual refresh

Phase 3 - Edit Day Availability:

1. Navigate to a schedule's detail page
2. Tap "Edit Hours" to open the Working Hours page
3. Tap a specific day (e.g., Monday)
4. Toggle availability on/off or modify time slots
5. Save and navigate back
6. Expected: Working Hours page AND detail page should reflect changes immediately without manual refresh

Date Overrides Empty State:

1. Navigate to a schedule that has NO date overrides
2. Tap on the "Date Overrides" section (should show "No date overrides set")
3. Expected: Should navigate to the edit override page where you can add new overrides

Error case: If network fails, UI should roll back to previous state and show error alert

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have checked if my changes generate no new warnings

Human Review Checklist

• Verify AvailabilityDetailScreen properly reads from React Query cache via useScheduleById (critical for cache updates to propagate)
• Verify edit-availability-hours route files properly read from React Query cache via useScheduleById
• Verify the optimistic update logic in useUpdateSchedule handles availability field correctly via spread operator
• Confirm the rollback in onError restores both detail and list caches correctly
• Verify Date Overrides section is clickable when empty (shows chevron, navigates to edit page)
• Test on iOS, Android, and browser extension
• Note: EventTypeDetail screen will be refactored in a subsequent phase

Link to Devin run: https://app.devin.ai/sessions/0e35f5cdab8943dabb66fc182e4241fe
Requested by: Dhairyashil Shinde (@dhairyashiil)