[FE-06] Implement optimistic updates with rollback for all admin CRUD mutations

[Leothosine]

Problem

MenuClient.tsx, GalleryClient.tsx, and ContactsClient.tsx all call queryClient.invalidateQueries() in mutation onSuccess handlers. This triggers a full server refetch on every toggle, delete, and status change. The user sees the whole table flash and reload. There is no rollback if a mutation fails.

Proposed Solution

1. Add onMutate callbacks that call queryClient.setQueryData() to immediately apply the expected change to the cache
2. Store the previous cache snapshot in onMutate context
3. In onError, call queryClient.setQueryData(previousSnapshot) to revert the change
4. Show per-row loading spinners (not table-level skeletons) during pending mutations using isPending and the item's id
5. Show a toast on mutation error with the server's error message

Acceptance Criteria

• Toggling a menu item's active state updates the UI instantly - no table refetch or flicker
• If the API call fails, the toggle reverts automatically and a toast shows the error
• Deleting a gallery image removes it from the list immediately and restores it on failure
• Updating a contact status changes the badge instantly
• Per-row spinner appears only on the affected row, not the whole table

[funds0033-cmyk]

pls i would like to work on this i have the skillset to deliver your request flawlessly kindly assign it to me

[Dev-sandy1]

Good day. Please can i work on these issue.

[Dev-sandy1]

Good day. Please can i work on these issue.

[soundsng]

Kindly assign me this issue. I can quickly resolve them and integrate it into existing systems. I am software developer with many years of experience.

[grantfox-oss]

🦊 GrantFox — @soundsng has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #274)
2. Your PR will be reviewed by the tosirano maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@soundsng's PR #300 was approved and merged by @Leothosine.

🏆 @soundsng: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (939 total points). Track your full progress on GrantFox.

👏 Great work, @soundsng! Keep contributing to tosirano.