fix: resolve all Mercy60-assigned issues (#653, #654, #663, #666)

[mercy60]

Summary

Resolves all four currently-open issues assigned to Mercy60:

• Closes BA-085 — Add prompt-template approval and audit metadata #653 — BA-085: Add prompt-template approval and audit metadata

  • PromptTemplate now records author, approval (status/approver/timestamp/review notes), effectiveAt, and rollback metadata.
  • Active-version selection only considers approved versions whose effective time has been reached and that haven't been rolled back.
  • New approveTemplate, rollbackTemplate, getActiveTemplate, and getTemplateAuditTrail APIs expose and record the governance trail.
  • Default templates carry baseline author/approval/effective metadata.

• Closes BA-086 — Improve prompt-injection detection beyond substring patterns #654 — BA-086: Improve prompt-injection detection beyond substring patterns

  • SecurityService.sanitisePrompt now runs layered detection:
    1. Normalisation: Unicode NFKC, case folding, zero-width/soft-hyphen removal, whitespace collapsing, repeated URL- and HTML-decoding, homoglyph transliteration.
    2. Direct layer against the normalised text (whitespace-tolerant patterns).
    3. Deobfuscated layer against separator-stripped text (e.g. i.g.n.o.r.e, d.e.v.e.l.o.p.e.r m.o.d.e) — only when separators were actually present to keep false positives low.
    4. Decoded layer for base64-encoded payloads.
    5. Multilingual patterns (FR/ES/DE override phrases).
  • detectPromptInjection exposes the matched reasons and layers.
  • Fixtures in security.service.spec.ts cover bypass attempts (case, spacing, zero-width, URL/HTML/base64 encoding, full-width, homoglyphs, multilingual) and false positives.

• Closes BA-095 — Make webhook idempotency durable and status-aware #663 — BA-095: Make webhook idempotency durable and status-aware

  • Process-local replay maps replaced with a durable store in DatabaseService (claimWebhookIdempotency / completeWebhookIdempotency / failWebhookIdempotency).
  • Claims carry a payload fingerprint, a processing status (in_progress / completed / failed), and an expiry, with atomic claim semantics (in-progress, completed, key-conflict, failed-retry, expired-reclaim).
  • The live webhook path (PaymentsController → AntiCheatService) now awaits the durable claim and fingerprints the raw payload; SecurityService and RedisService delegate to the same store (with the old in-memory behavior as a fallback when no DatabaseService is injected, e.g. isolated tests).

• Closes BA-098 — Add durable webhook delivery records and outbox processing #666 — BA-098: Add durable webhook delivery records and outbox processing

  • New durable outbox in DatabaseService: enqueueWebhookDelivery (stored before delivery), claimDueWebhookDeliveries (atomic claims), completeWebhookDelivery, recordWebhookDeliveryFailure (resumable retrying + nextRetryAt), and inspectable terminal failed records (getTerminalWebhookFailures, listWebhookOutbox).
  • PaymentsService gains enqueueWebhook, deliverDueWebhooks, getWebhookDeliveryRecord, listWebhookOutbox, and getTerminalWebhookFailures; deliverWebhookWithRetry now drives delivery through the outbox (also repairing the previously mangled constructor/imports in payments.service.ts).

Verification

• 4 new spec files, 55 tests, all passing:
  • security.service.spec.ts (injection fixtures + durable idempotency)
  • database/database.service.spec.ts (claim semantics + outbox lifecycle)
  • payments/payments.service.spec.ts (outbox delivery + webhook processing regression)
  • ai/prompt-template.service.spec.ts (approval/effective-time/rollback/audit)
• tsc --noEmit shows zero errors in every changed file (project-wide error count dropped 320 → 289; the remaining errors are pre-existing in unrelated files).
• No new lint errors introduced (pre-existing no-var-requires / unused-import warnings in touched-but-unchanged lines remain).

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