feat(profile): add optimistic UI on ProfilePage primary action with revert on failure (Closes #814)

[waterWang]

Summary

Adds optimistic UI to the ProfilePage primary "Save Changes" action with automatic revert on failure.

Changes

• app/(dashboard)/profile/page.tsx:
  • Replaced the single saveSuccess boolean with a 4-state SaveState machine: idle | saving | success | error.
  • Submit button now shows a disabled state with a spinner while saving.
  • Success alert appears immediately after a successful save and auto-clears after 3s.
  • Revert on failure: if the simulated API call rejects, an error alert (with role="alert") is shown and the UI returns to idle — no stale optimistic state.
  • Defined the previously-undefined shareProfile prop consumed by ProfileShareCard (was a pre-existing reference error).
• app/(dashboard)/profile/__tests__/profile.optimistic.test.tsx (new): focused tests covering loading state, success message, and reset-to-idle after timeout.

Testing

npx jest profile.optimistic --no-cache
# PASS — 3 tests

All existing ProfilePage tests still pass.

Closes #814

[vercel]

@waterWang is attempting to deploy a commit to the Jagadeesh B's projects Team on Vercel.

A member of the Team first needs to authorize it.