feat(layout): migrate to full-width topbar with mobile drawer navigation

Move topbar outside the grid container as a standalone sticky header
(Shopify/Stripe pattern). Sidebar and icon bar use position:sticky
relative to topbar height. Mobile uses drawer pattern with backdrop,
focus trap, ESC close, and scroll lock. Tenant branding moved from
sidebar header into the topbar.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/css/components/app-details.css

@@ -121,7 +121,7 @@
 
   .app-details-container .app-details-titlebar {
     position: sticky;
-    top: 37px;
+    top: var(--app-topbar-height);
     z-index: 10;
     padding-block-start: calc(var(--app-spacing) * 2);
     background: var(--app-background-color);