fix(audit): kill fake install cmds + dead demo CTA; production fonts; scoped error boundary; admin bootstrap seed

Full-site fake-data audit findings:
- SetupWizard showed a curl|sh installer (get.corrosionmgmt.com) and a
  'corrosion-agent' binary that don't exist -> real host-agent commands
- 'View live demo' CTA on 5 marketing pages linked to a login, not a
  demo -> honest 'Sign in'
- Google Fonts @import was silently dropped from the production CSS
  bundle (mid-bundle @import) -> <link> tags in index.html; prod was
  shipping system fallback fonts
- App-root ErrorBoundary bricked the entire SPA (incl. marketing) on a
  single failed fetch until manual reload -> resets on route change +
  content-scoped boundary inside DashboardLayout so nav chrome survives
- Status page KPIs showed fake zeros while the fetch failed -> em dash
- Login lacked the forgot-password link (flow already existed end-to-end)
- AdminSeedService: fresh DB had schema but no login possible; seeds
  super-admin + license from ADMIN_* env when users table is empty

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/layout/DashboardLayout.vue

@@ -14,6 +14,7 @@ import { useThemeGame } from '@/composables/useThemeGame'
 import { useGameProfile } from '@/config/gameProfiles'
 import type { NavSection, NavItemDef } from '@/config/gameProfiles'
 import { safeDate } from '@/utils/formatters'
+import ErrorBoundary from '@/components/ErrorBoundary.vue'
 import Logo from '@/components/ds/brand/Logo.vue'
 import Badge from '@/components/ds/core/Badge.vue'
 import StatusDot from '@/components/ds/core/StatusDot.vue'
@@ -284,9 +285,11 @@ const themeIcon = computed(() => theme.value === 'dark' ? 'sun' : 'moon')
         </div>
       </header>
 
-      <!-- Page content -->
+      <!-- Page content — boundary keeps sidebar/topbar alive when a view fails -->
       <main class="app__content">
-        <RouterView />
+        <ErrorBoundary variant="content">
+          <RouterView />
+        </ErrorBoundary>
       </main>
     </div>
   </div>