Implement User Actions (Ban / Reactivate / Delete / Reset Password)

**Description:**

Add actions:

- Ban user
- Reactivate user
- Delete user
- Reset password

Must include:

- Confirmation modal
- Toast notification
- Error handling

**Checklist:**

- [ ] Ban endpoint
- [ ] Reactivate endpoint
- [ ] Delete endpoint
- [ ] Reset password endpoint
- [ ] Confirmation dialog

No files, tests, or entry points are named. Start by locating the user-management screen and existing API action patterns; implement ban, reactivate, delete, and password-reset actions with confirmation, success toasts, and error handling. Done means all four endpoints and the confirmation dialog are complete.

Written by the indexing model from the issue text.