Show a progress bar and live log while Hammerhead, edges and sites update

The updater reports each step (checking, downloading with percent, verifying, installing, restarting).
Edges and sites send that progress and their log with their reports; Hammerhead serves it to a dialog
that opens when an update starts, and keeps its own last update log on disk across the restart.

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

server.go

@@ -99,7 +99,10 @@ func (s *Server) Handler() http.Handler {
 	mux.HandleFunc("POST /api/admin/settings/test-mail", s.withServerAdmin(s.testMail))
 	mux.HandleFunc("GET /api/admin/update", s.withServerAdmin(s.checkUpdate))
 	mux.HandleFunc("POST /api/admin/update/apply", s.withServerAdmin(s.applyUpdate))
+	mux.HandleFunc("GET /api/admin/update/status", s.withServerAdmin(s.updateStatus))
 	mux.HandleFunc("GET /api/versions", s.withUser(s.latestVersions))
+	mux.HandleFunc("GET /api/edges/{id}/update/log", s.withServerAdmin(s.edgeUpdateLog))
+	mux.HandleFunc("GET /api/orgs/{org}/sites/{id}/update/log", s.withOrg(true, s.siteUpdateLog))
 	mux.HandleFunc("POST /api/edges/{id}/update", s.withServerAdmin(s.updateEdge))
 	mux.HandleFunc("POST /api/orgs/{org}/sites/{id}/update", s.withOrg(true, s.updateSite))
 	mux.HandleFunc("GET /api/admin/audit", s.withServerAdmin(func(w http.ResponseWriter, r *http.Request, p *principal) {