Persist payment-webhook dedup; declare BTCPay required; scope CORS

Replace the in-memory dedup Sets in the BTCPay and Zaprite webhook
handlers (and the BTCPay rescan path) with a persistent JSON-backed
store (server/webhook-dedup.js). The in-memory sets were cleared on
restart, so a duplicate webhook delivery straddling a relay restart
could double-credit (BTCPay) or double-extend a subscription (Zaprite).
The store atomically writes /data/processed-webhooks.json, namespaces
keys per rail (storeId|invoiceId vs zaprite:orderId), and prunes
entries older than 180 days (safely beyond any retry window).

Also:
- BTCPay is a required running dependency (operator decision). Config
  was already optional:false/kind:'running'; corrected the contradictory
  "optional" comment in the manifest to match.
- Scope cors() to /relay/* only — off /admin/* and the same-origin
  dashboard, which don't need permissive CORS.
- Add money-path unit tests (commitCredit/refundCredit/applyTierPromotion)
  and webhook-dedup tests (incl. the survives-a-restart guarantee).
- Fix two AGENTS.md auth-doc drifts; refresh Current state.

Version 0.2.125 -> 0.2.126.

startos/versions/v0.2.126.ts

@@ -0,0 +1,12 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_126 = VersionInfo.of({
+  version: '0.2.126:0',
+  releaseNotes: {
+    en_US: 'Persist payment-webhook dedup across restarts (no double-credit/double-extend); declare BTCPay a required dependency; scope CORS to /relay/*; add money-path + webhook-dedup tests; doc fixes',
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})