Tell non-admins why the console is off-limits instead of bouncing them to the dashboard

coordinator/internal/transport/http/ui_admin.go

@@ -26,12 +26,14 @@ var adminUserActions = map[string]bool{
 }
 
 // requireAdmin gates a route on the session caller being an admin. It runs
-// inside withUISession, which has already stamped the requester. A non-admin is
-// sent back to the dashboard rather than shown the panel.
+// inside withUISession, which has already stamped the requester. A signed-in
+// non-admin is told why (and bounced to the login with the message); an
+// unauthenticated caller never gets here — the gate has already sent them to
+// the login page with the intended destination.
 func requireAdmin(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if req, ok := authctx.From(r.Context()); !ok || !req.IsAdmin() {
-			http.Redirect(w, r, "/ui", http.StatusSeeOther)
+			http.Redirect(w, r, "/ui/login?error=admin+role+required", http.StatusSeeOther)
 			return
 		}
 		next.ServeHTTP(w, r)

coordinator/internal/transport/http/ui_admin_internal_test.go

@@ -30,15 +30,15 @@ func TestRequireAdminAllowsAdminOnly(t *testing.T) {
 		t.Error("admin must reach the handler")
 	}
 
-	// Plain user is redirected to the dashboard.
+	// Plain user is redirected to the login with the reason.
 	reached = false
 	rec := httptest.NewRecorder()
 	h.ServeHTTP(rec, adminReq(t, "user"))
 	if reached {
 		t.Error("non-admin must not reach the handler")
 	}
-	if rec.Code != http.StatusSeeOther || rec.Header().Get("Location") != "/ui" {
-		t.Errorf("non-admin got %d -> %q, want 303 -> /ui", rec.Code, rec.Header().Get("Location"))
+	if rec.Code != http.StatusSeeOther || rec.Header().Get("Location") != "/ui/login?error=admin+role+required" {
+		t.Errorf("non-admin got %d -> %q, want 303 -> login with the admin-required error", rec.Code, rec.Header().Get("Location"))
 	}
 }