Add Storage, Users, Secrets, Webhooks, Scheduled tasks, Audit log screens

Full management surfaces for the platform-admin tenant, mirroring the
existing Tenants pattern (DataTable + row actions + create/edit dialogs +
ConfirmDialog for destructive ops, all data-action tagged for the
command bus, useRegisterAdminContext publishing for the assistant).

- Storage (/storage): backends + credentials. Write-only secret fields,
  Validate/Activate/Deactivate/Set-default/Mark-degraded/Maintenance.
- Users (/users): tabs for Users, Invitations, Roles. Per-user View
  drawer with profile, role add/remove, API keys (one-time reveal on
  create), usage + quota.
- Secrets (/secrets): /api/v1/admin/secrets — create/rotate/rollback,
  versions dialog, enable/disable, generate-value helper.
- Webhooks (/webhooks): CRUD, pause/resume, regenerate-secret with
  one-time reveal, send test event, deliveries dialog.
- Scheduled tasks (/scheduled-tasks): cron CRUD, run-now trigger,
  enable/disable, expandable run history.
- Audit log (/activity): replaces the empty stub. Filter by severity,
  resource type, date range; click for full JSON detail.

All endpoints are hand-rolled HTTP because most aren't covered by the
generated OpenAPI typed paths yet — switch to arcadia.typed.* when the
backend wires them into OpenApiSpex.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/components/layout/app-shell.tsx

@@ -20,6 +20,11 @@ import {
   HelpCircle,
   Menu,
   Play,
+  HardDrive,
+  Users as UsersIcon,
+  KeyRound,
+  Webhook as WebhookIcon,
+  CalendarClock,
   // CREMA:NAV-ICONS
 } from "lucide-react"
 
@@ -88,6 +93,11 @@ type NavItem = {
 const navItems: NavItem[] = [
   { to: "/", icon: LayoutDashboard, label: "Overview", end: true },
   { to: "/tenants", icon: Building2, label: "Tenants" },
+  { to: "/storage", icon: HardDrive, label: "Storage" },
+  { to: "/users", icon: UsersIcon, label: "Users" },
+  { to: "/secrets", icon: KeyRound, label: "Secrets" },
+  { to: "/webhooks", icon: WebhookIcon, label: "Webhooks" },
+  { to: "/scheduled-tasks", icon: CalendarClock, label: "Scheduled" },
   { to: "/activity", icon: Activity, label: "Audit log" },
   { to: "/ai", icon: Bot, label: "AI" },
   { to: "/settings", icon: Settings, label: "Settings" },