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/config/paths.ts

@@ -54,6 +54,19 @@ const pathsConfig = {
       index: `${ADMIN_PREFIX}/customers`,
       customer: (id: string) => `${ADMIN_PREFIX}/customers/${id}`,
     },
+    meshes: {
+      index: `${ADMIN_PREFIX}/meshes`,
+      mesh: (id: string) => `${ADMIN_PREFIX}/meshes/${id}`,
+    },
+    sessions: {
+      index: `${ADMIN_PREFIX}/sessions`,
+    },
+    invites: {
+      index: `${ADMIN_PREFIX}/invites`,
+    },
+    audit: {
+      index: `${ADMIN_PREFIX}/audit`,
+    },
   },
   marketing: {
     pricing: "/pricing",