feat: one-page panel - shell with Машины, Терминал and Настройки, pages as fragments, forms sent in place

internal/server/web/static/app.css

@@ -259,3 +259,6 @@ input.sw:disabled { opacity: .45; cursor: not-allowed; }
 @supports not selector(::-webkit-scrollbar) {
   * { scrollbar-width: thin; scrollbar-color: rgba(62, 68, 78, calc(var(--sb) * .9)) transparent; }
 }
+
+/* The one-page shell: the header's current view. */
+header.topbar nav a.on { color: var(--text); }