Admin name at init, token rotation, read-only forms, token role presets

- stewardd init asks for the first administrator's name on a terminal.
- Tokens can be rotated (steward token rotate, POST /tokens/{id}/rotate,
  Rotate in the web UI), with a grace period for the old secret, as in
  Jarl. Schema migration 2 adds the token columns.
- Read-only users see the settings and a subnet's settings locked,
  instead of editable fields without a Save button.
- The New token dialog only offers roles within what the user may do.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/server/routes.go

@@ -28,6 +28,7 @@ func (s *Server) routes() {
 	m.HandleFunc("POST "+p+"/me/tokens", s.authed(s.createOwnToken))
 	m.HandleFunc("GET "+p+"/tokens", s.authed(s.listAllTokens))
 	m.HandleFunc("DELETE "+p+"/tokens/{id}", s.authed(s.revokeToken))
+	m.HandleFunc("POST "+p+"/tokens/{id}/rotate", s.authed(s.rotateToken))
 	m.HandleFunc("GET "+p+"/users", s.authed(s.listUsers))
 	m.HandleFunc("POST "+p+"/users", s.authed(s.createUser))
 	m.HandleFunc("PATCH "+p+"/users/{id}", s.authed(s.updateUser))