feat(webhooks): implement subscription topic filtering (#119)

[Ebenezer199914]

Core Feature — Webhook Subscription Topic Filtering

• Add webhookMatchesTopic() with exact and wildcard (transaction.*) matching
• Export ALLOWED_EVENTS and WILDCARD_TOPICS constants from merchantWebhook model
• Add MerchantWebhookModel.listAvailableTopics() with event descriptions
• Add MerchantWebhookModel.findActiveByUserIdAndTopic() for topic-aware lookup
• Update MerchantWebhookService.dispatchEvent() to use topic-aware fan-out
• Add MerchantWebhookService.listTopics() helper
• Add GET /api/merchant/webhooks/topics route exposing available topics
• Add migration 20260629_webhook_topic_filtering.sql:
  • GIN index on merchant_webhooks.events for fast topic queries
  • CHECK constraint allowing 'transaction.*' wildcard alongside concrete events

Bug Fixes

• src/stellar/webhooks.ts: fix memo-based transaction lookup
  • text memos fall through to reference-number lookup first, as expected
  • findByReferenceNumber return handled as array or single object
  • Remove stellar_hash from patchMetadata (not expected by consumers)
• src/routes/webhooks.ts: add setup_url to 500 response when WEBHOOK_SECRET unset
• src/routes/tests/webhooks.test.ts: mock TransactionModel + ingestRateLimiter so tests no longer require a live database/Redis connection
• src/stellar/sep02.ts: restore domain check in lookupByName; fix 'q is required' error message; remove orphaned return/brace fragment (pre-existing syntax error)
• src/queue/accountMergeWorker.ts: fix capturePersistentFailure call signature (pass CaptureOptions object instead of raw Job — pre-existing type error)

Tests

• New: src/services/tests/merchantWebhook.topic-filtering.test.ts
  • webhookMatchesTopic() exact and wildcard coverage
  • ALLOWED_EVENTS / WILDCARD_TOPICS constant assertions
  • listAvailableTopics() shape and description completeness
  • create/update validation with wildcard acceptance
  • findActiveByUserIdAndTopic() filters inactive and non-matching webhooks
  • dispatchEvent() topic-aware fan-out and no-match short-circuit
• All 77 webhook tests pass (7 suites, 0 failures)
• All 23 SEP-02 federation tests pass
• TypeScript build clean (0 errors)

Description

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Related Issue

Fixes #(issue number)

Type of Change

• Bug fix
• New feature
• Documentation update
• Code refactoring
• Performance improvement

Changes Made

Testing

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Checklist

• Code follows project style
• Self-reviewed my code
• Commented complex code
• Updated documentation
• No new warnings
• Added tests (if applicable)

Screenshots (if applicable)

Additional Notes

closes feat(webhooks): implement subscription topic filtering (#119)
#126

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