Wire operator Integrations page + capability-gating framework

Completes the arcadia-admin operator surface for the integration registry and
the capability/route-guard framework it depends on.

- Integration registry: route + Data-group nav entry + `platform.integrations`
  capability; the in-app client now delegates to the shared
  `@crema/integration-registry-client` lib (vite alias + tsconfig); the
  operator Integrations page (committed earlier) is now reachable.
- Capability gating: capabilities map + route-guard + jwt helpers + the
  apps/plan/entitlements routes and supporting tenants/session changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/routes/plan.tsx

@@ -0,0 +1,40 @@
+// Tenant subscription + billing — placeholder. Real surface lists the
+// active plan, renewal date, invoices, and payment method for the
+// active tenant. Data source not wired yet.
+
+import { CreditCard } from "lucide-react"
+import { AppShell } from "~/components/layout/app-shell"
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+  CardTitle,
+} from "~/components/ui/card"
+
+export default function PlanRoute() {
+  return (
+    <AppShell>
+      <div className="flex items-center gap-3">
+        <div className="flex size-10 items-center justify-center rounded-lg bg-primary/10 text-primary">
+          <CreditCard className="size-5" />
+        </div>
+        <div>
+          <h1 className="text-2xl font-semibold">Plan</h1>
+          <p className="text-sm text-muted-foreground">
+            Your tenant's subscription, billing details, and invoice history.
+          </p>
+        </div>
+      </div>
+      <Card>
+        <CardHeader>
+          <CardTitle>Coming soon</CardTitle>
+          <CardDescription>
+            Billing is not yet wired to a payment provider on this deployment.
+          </CardDescription>
+        </CardHeader>
+        <CardContent />
+      </Card>
+    </AppShell>
+  )
+}