Allow users to change their names (and admins if isWkorgInstance==false)

[fm3]

URL of deployed dev instance (used for testing):

• https://___.webknossos.xyz

Steps to test:

• abc

TODOs:

• [x] Backend
  • [x] re-use existing PATCH users route
  • [x] Update names of all multiusers
  • [x] Check permissions as discussed in https://scm.slack.com/archives/C5AKLAV0B/p1764071136741679
• [ ] Frontend
  • [x] Name change form in account/profile
  • [x] Name change in user list for admins (if features.isWkorgInstance==false)
    • [ ] fix: selected users after modal was closed
    • [ ] fix: update table after modal was closed
    • [ ] code quality

Issues:

• fixes #9093
• follow-up: #9105

---

• [ ] Added changelog entry (create a $PR_NUMBER.md file in unreleased_changes or use ./tools/create-changelog-entry.py)
• [ ] Added migration guide entry if applicable (edit the same file as for the changelog)
• [ ] Updated documentation if applicable
• [ ] Adapted wk-libs python client if relevant API parts change
• [ ] Removed dev-only changes like prints and application.conf edits
• [ ] Considered common edge cases
• [ ] Needs datastore update after deployment