Add private Business push delivery and provider receipts

[sridharkalaibala]

Business sessions can opt a phone into generic push alerts for new Inbox entries. Registrations are private and session-bound; delivery rechecks current session/password generation, branch membership, financial permission and notification preferences. The worker uses durable event/device records, retry delays and provider receipts. A delayed invalid-device receipt cannot delete a newer registration.

The fixed Expo transport sends no sales amounts, account credentials, URLs or approval commands. Stable collapse/tag IDs reduce visible duplicates after ambiguous network failures. Provider acceptance is recorded separately from user/device delivery; no exactly-once promise is made. Delivery stays disabled unless the owning deployment configures its project and secret access token. Community operators must not receive Posnic's project credential; an official-app relay is still pending.

Local validation: 12 access/reporting/notification-route integration tests, five notification integration tests, five push integration tests, two transport tests, two worker tests, and 24 README/sync checks pass. Changed services pass lint and attribution. API docs report 730 endpoints. Provider calls are mocked; no actual push was sent and no CI expansion was added.

Stacks on #1009. Native app registration is in the companion mobile push branch. Production credentials, physical devices and Community relay qualification remain required.

[sridharkalaibala]

The complete Business companion stack, including this change, is integrated into develop through #1023. All checks, including CodeQL, passed before merge. Closing this superseded stacked PR.