Admin UI: allow administrators to change/reset another user's password

### Bug description

Currently (using Superset 6.0.0rc2) there is no straightforward, documented way for a Superset admin to change or reset another user's password from the web UI. This makes account recovery and user management harder for operators and requires server-side or DB access to reset passwords.

### Why this matters
Operators and helpdesk staff need a safe in-product way to reset user passwords without direct DB edits or ad-hoc scripts. Relying on manual DB changes is error-prone and a security/operational burden.

### Expected behavior
In Security → List Users (or on the "edit users" page), a site admin should be able to click "Reset password" (or similar), provide a new password, confirm and save; the user's password is updated and they can sign in with the new credentials

Optionally: audit log entry created when an admin changes someone else's password for traceability.

Action requires an Admin role (or a configurable permission).

### Workaround
(documented so admins can use it while the feature is implemented)

```
docker exec -it superset_app superset fab reset-password \
--username "Joe User" --password "password"
```

### Screenshots/recordings

_No response_

### Superset version

master / latest-dev

### Python version

3.10

### Node version

16

### Browser

Chrome

### Additional context

Superset Version 6.0.0rc2

### Checklist

- [x] I have searched Superset docs and Slack and didn't find a solution to my problem.
- [x] I have searched the GitHub issue tracker and didn't find a similar bug report.
- [ ] I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

Start with the Security → List Users and “edit users” entry points, then review the existing `superset fab reset-password` workaround and its password-update behavior. Done means an Admin can reset another user’s password from the web UI with confirmation, the user can sign in with it, and any implemented audit entry is recorded.

Written by the indexing model from the issue text.