feat: extract admin account management rework from PR 124 (#138)

* feat: reorganize admin panel around accounts

* feat: expand admin customer account controls

* feat: add admin account detail management

* fix: remove unused admin account icon import

* refactor: design critique fixes for account pages

- Admin accounts: replace dense card grid with compact DataTable
- Account settings: remove redundant hero card, stat grid, header pills
- Fix bg-accent (orange) misuse on decorative elements across 7 files
- Add ConfirmButton for destructive actions (deactivate, remove member)
- Replace single-field modals with inline editing (plan, trial)
- Add contextual help: display code tooltip, improved empty states
- Non-owner aside explanation for hidden owner-only sections
- Admin sidebar: group 11 items into 5 labeled sections
- Rename UsersPage.tsx → AccountsPage.tsx to match route
- Fix border radius consistency, hide zero-count badges

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

* fix: use get_admin_db for all new admin account endpoints

All admin endpoints query across tenants without a tenant context.
get_db (app-role, subject to RLS) was never imported and would crash
at runtime — replace all 6 occurrences with get_admin_db (BYPASSRLS).

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

---------

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

frontend/src/router.tsx

@@ -65,7 +65,8 @@ const DiagramEditorPage = lazyWithRetry(() => import('@/pages/NetworkDiagrams/Di
 // Admin pages
 const AdminLayout = lazyWithRetry(() => import('@/components/admin/AdminLayout'))
 const AdminDashboardPage = lazyWithRetry(() => import('@/pages/admin/DashboardPage'))
-const AdminUsersPage = lazyWithRetry(() => import('@/pages/admin/UsersPage'))
+const AdminAccountsPage = lazyWithRetry(() => import('@/pages/admin/AccountsPage'))
+const AdminAccountDetailPage = lazyWithRetry(() => import('@/pages/admin/AccountDetailPage'))
 const AdminUserDetailPage = lazyWithRetry(() => import('@/pages/admin/UserDetailPage'))
 const AdminInviteCodesPage = lazyWithRetry(() => import('@/pages/admin/InviteCodesPage'))
 const AdminAuditLogsPage = lazyWithRetry(() => import('@/pages/admin/AuditLogsPage'))
@@ -227,7 +228,9 @@ export const router = sentryCreateBrowserRouter([
         ),
         children: [
           { index: true, element: page(AdminDashboardPage) },
-          { path: 'users', element: page(AdminUsersPage) },
+          { path: 'accounts', element: page(AdminAccountsPage) },
+          { path: 'accounts/:accountId', element: page(AdminAccountDetailPage) },
+          { path: 'users', element: page(AdminAccountsPage) },
           { path: 'users/:userId', element: page(AdminUserDetailPage) },
           { path: 'invite-codes', element: page(AdminInviteCodesPage) },
           { path: 'audit-logs', element: page(AdminAuditLogsPage) },