feat(testing): add isolated Stryker mutation configs and queue worker test suites

[ShantelPeters]

📌 Overview

This PR resolves SIGBUS worker process failures during StrykerJS mutation testing on Node v24 / macOS Apple Silicon by introducing standalone, isolated Jest configurations (jest.stryker.config.js and jest.stryker.queue.config.js). It also expands unit test coverage for queue worker operations and core services (feeService, transactionService, syncWorker, syncQueue).

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🎯 Key Changes

1. Isolated Jest Configurations for StrykerJS:

   • Added jest.stryker.config.js targeting core services.
   • Added jest.stryker.queue.config.js targeting queue workers.
   • Configured isolatedModules: true and maxWorkers: 1 in ts-jest to disable worker thread spawning during mutation test execution.
   • Removed top-level projects array inheritance to avoid duplicate worker initialization inside Stryker sandboxes.

2. Expanded Test Suites:

   • src/services/__tests__/feeService.test.ts: Complete unit tests for fee calculation, active configuration retrieval, audit logging, and CRUD operations.
   • src/services/__tests__/transactionService.test.ts: Complete unit tests for transaction lifecycle management.
   • src/tests/queue/syncQueue.test.ts: Edge-case unit tests covering options fallbacks (priority, delay, jobId), optional chaining, and queue health metrics (getSyncQueueStats).
   • src/tests/queue/syncWorker.nats.test.ts & src/tests/queue/syncWorker.test.ts: Test coverage for BullMQ and NATS JetStream sync message handlers.

3. Type Safety & Tracing Fixes:

   • Explicitly typed Datadog tracing spans in src/queue/syncWorker.ts to ensure compatibility across OpenTelemetry/Datadog interfaces.

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🧪 Verification & Results

1. Standalone Jest Test Executions

• Services Suite: 2 passed, 2 total (30/30 unit tests green)

  npx jest --config jest.stryker.config.js
  

CLOSES #1836

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