Add admin user management

public/admin.css

@@ -274,6 +274,54 @@ label { display: grid; gap: 6px; color: var(--muted); font-size: 13px; }
   background: #edf3ef;
   color: var(--ink);
 }
+.admin-users-settings {
+  margin-top: 14px;
+}
+.admin-user-form {
+  grid-column: 1 / -1;
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 10px;
+}
+.admin-user-form label:nth-child(3),
+.admin-user-form button {
+  grid-column: 1 / -1;
+}
+.admin-users-list {
+  grid-column: 1 / -1;
+  display: grid;
+  gap: 8px;
+}
+.admin-user-item {
+  display: grid;
+  grid-template-columns: minmax(0, 1fr) auto auto auto auto;
+  align-items: center;
+  gap: 8px;
+  padding: 9px 10px;
+  border: 1px solid var(--line);
+  border-radius: 8px;
+  background: #fff;
+}
+.admin-user-item div {
+  display: grid;
+  gap: 2px;
+  min-width: 0;
+}
+.admin-user-item span {
+  color: var(--muted);
+  font-size: 12px;
+}
+.password-mask {
+  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
+  letter-spacing: 1px;
+}
+.admin-user-item button:disabled {
+  opacity: .45;
+  cursor: not-allowed;
+}
+#adminUsersStatus {
+  grid-column: 1 / -1;
+}
 .list-tools {
   padding: 10px 14px;
   border-bottom: 1px solid var(--line);