fix(adminui): clear stale one-time key banner on delete; modal backdrop no longer overruns viewport (#631)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/wwwroot/css/site.css

@@ -48,3 +48,22 @@
     flex: 0 0 18px;
     width: 18px;
 }
+
+/* Modal sizing (#631). Bootstrap sizes .modal-backdrop with 100vw/100vh, and 100vw includes the
+   scrollbar gutter, so on a tall form (Configure driver / Modbus) the backdrop overran the viewport
+   and produced a page-level horizontal scrollbar. Pin it with inset:0 instead (no vw/vh), and keep
+   the dialog inside the viewport. These modals are hand-rolled (display:block, no Bootstrap JS). */
+.modal-backdrop {
+    inset: 0;
+    width: auto;
+    height: auto;
+}
+
+.modal {
+    overflow-x: hidden;
+    overflow-y: auto;
+}
+
+.modal-dialog {
+    max-width: min(var(--bs-modal-width, 500px), calc(100vw - 2rem));
+}