FR-0003 — Orchestrate PayPal Sandbox checkout

Statement: The server shall reconstruct the order amount from the trusted catalog and create and capture orders only through PayPal Sandbox. Rationale: Browser-provided prices and production payment endpoints are outside the trust boundary. Status: Proposed; implementation candidate under the bootstrap override. Owner: Architecture. Source Feature: ESHOPV1-FT-3 and its Sandbox checkout acceptance outcome. C4 element: PayPal BFF. Task: ESHOPV1-TS-3. Acceptance evidence: Payment tests at application commit 7fd6b88; end-to-end Sandbox evidence is blocked by runtime credentials.