feat(push): owner-only gate and subscription body validation (T10)

isOwner compares the session email to the configured owner; the body
matches the browser PushSubscription.toJSON() shape, reporter resolved
server-side.

server/utils/isOwner.ts

@@ -0,0 +1,7 @@
+// Owner-only gate for Web Push (T10). v1 notifies a single configured owner
+// (DESIGN G3); the owner email comes from runtime config server-side. If no
+// owner is configured, nobody qualifies — push enrolment stays closed.
+export function isOwner(email: string | undefined, ownerEmail: string | undefined): boolean {
+  if (!email || !ownerEmail) return false
+  return email.toLowerCase() === ownerEmail.toLowerCase()
+}

server/utils/pushSubscriptionInput.ts

@@ -0,0 +1,16 @@
+import { type } from 'arktype'
+
+// Validated push-subscription body — the browser's PushSubscription.toJSON()
+// shape (T10/F8). Never trusted from the client beyond these constraints; the
+// reporter is resolved server-side from the session, not sent here.
+const nonEmptyKey = type('string').narrow((s, ctx) => s.length > 0 || ctx.reject('a non-empty key'))
+
+export const PushSubscriptionInput = type({
+  endpoint: 'string.url',
+  keys: {
+    p256dh: nonEmptyKey,
+    auth: nonEmptyKey,
+  },
+})
+
+export type PushSubscriptionInputData = typeof PushSubscriptionInput.infer