feat(web): admin backoffice — meshes, sessions, invites, audit, overview

Four new admin routes backed by the mesh API modules:

- /admin/meshes — paginated data-table (name, owner, tier, transport,
  members, created). Tier + transport multiSelect filters.
- /admin/meshes/[id] — detail page: owner row + 4 live sections
  (members, presences, invites, last 50 audit events).
- /admin/sessions — live Claude Code WS presences. Status filter,
  pulse dot for working sessions, disconnected badge.
- /admin/invites — invite tokens w/ status derived client-side
  (active/revoked/expired/exhausted).
- /admin/audit — metadata-only event log, event-type + mesh + date
  filters.

Overview page at /admin rewritten to 6 summary cards (users, orgs,
customers, meshes, sessions, messages 24h) joining the base
/admin/summary and /admin/summary/mesh endpoints.

Sidebar navigation gains a second "mesh" group with the four new entries.
paths.ts extended with admin.meshes / sessions / invites / audit.

All UI reuses @turbostarter/ui-web/data-table — columns.tsx + thin
*-data-table.tsx wrapper per the existing users pattern.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/app/[locale]/admin/layout.tsx

@@ -35,6 +35,31 @@ const menu = [
       },
     ],
   },
+  {
+    label: "mesh",
+    items: [
+      {
+        title: "meshes",
+        href: pathsConfig.admin.meshes.index,
+        icon: Icons.Share,
+      },
+      {
+        title: "sessions",
+        href: pathsConfig.admin.sessions.index,
+        icon: Icons.Activity,
+      },
+      {
+        title: "invites",
+        href: pathsConfig.admin.invites.index,
+        icon: Icons.Link,
+      },
+      {
+        title: "audit",
+        href: pathsConfig.admin.audit.index,
+        icon: Icons.ScrollText,
+      },
+    ],
+  },
 ];
 
 export default async function AdminLayout({