A shop can be renamed and, while empty, removed - from head office

The display name was always meant to be editable and the slug frozen;
until now neither had a way in. PATCH /api/sites/{site} takes a name
and a timezone (manager and above), DELETE removes an empty shop
(owner). The shop drawer in head office gets both, with the short name
shown read-only and the reason beside it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KGcjxF1cNLcuwc3DAPcnfj

server/internal/api/api.go

@@ -159,6 +159,9 @@ type Store interface {
 	// one opened by mistake - and returns its broker username. A shop with
 	// history is closed, not deleted.
 	DeleteEmptySite(ctx context.Context, clientID, siteID string) (string, error)
+	// UpdateSite changes what a person reads - the name, the timezone. Never
+	// the slug: the shop PC and the broker ACL are keyed on it.
+	UpdateSite(ctx context.Context, clientID, siteID string, in SiteUpdate) (SiteHealth, error)
 
 	// --- enrolment ---
 	RedeemEnrolment(ctx context.Context, hash []byte) (Enrolment, error)
@@ -301,6 +304,7 @@ func (s *Server) Routes() *http.ServeMux {
 	mux.HandleFunc("GET /api/sites", s.authed(s.handleSites))
 	mux.HandleFunc("POST /api/sites", s.authed(s.handleCreateSite))
 	mux.HandleFunc("DELETE /api/sites/{site}", s.authed(s.handleDeleteSite))
+	mux.HandleFunc("PATCH /api/sites/{site}", s.authed(s.handleUpdateSite))
 
 	// Cameras, onboarded from head office. The shop PC still does the
 	// connecting - it is the only thing on the camera's network - so these