PayPal app and compatibility adapter

The package owns its Manifest and src/ implementation: Orders v2 wire calls, account/admission mapping, receipt interpretation and webhook signature verification. The payment core retains its shared attempt ledger, reservations, jobs, receipt policies and remote provider contract; it references these app-owned files without copying them.

Execution boundary: this legacy adapter is still host-native to preserve already configured PayPal attempts and the existing webhook route. Folder ownership is not a sandbox. New providers use the generic remote payment contract and a separate approved service; private Shopware Payments remains in its private repo. Do not mark this compatibility bridge as a sandboxed third-party Rust runtime. A complete remote cutover needs a migration of existing attempts and provider configuration, plus signature/reconciliation compatibility.

Run the registered payments suite for local OAuth/order/capture/refund/webhook fixtures, including restart/idempotency and exact amount binding. It does not charge money or prove a configured live merchant account.