New /profile route (nav link between Admin and Logout) with two
independent forms, both requiring the current password before
applying a change:
- Change password: standard current/new/repeat flow, same password
strength rules as registration.
- Change email: re-checks the new address isn't already taken (avoids
a 500 from the unique constraint), then marks the account
unverified and re-sends the confirmation email via the existing
EmailVerifier/verify-email flow, same as registration. The current
session stays logged in, but the user needs to verify the new
address before their next login (UserChecker already blocks
unverified accounts).