Confirm error handling refactor addresses transaction rollback concerns

[Copilot]

Review response to feedback on PR #62 regarding error handling in handleCompleteHeat. The original code threw errors with _statusCode inside transactions, which the middleware didn't recognize, potentially resulting in incorrect status codes.

Changes Verified

The refactor in commit 2633248 correctly addresses the concern:

• Transaction handling: Uses withResultTransaction wrapper that intercepts err() results and rolls back via sentinel value
• Error propagation: Returns Result<T, E> from transaction instead of throwing
• Status mapping: Checks txResult.isErr() outside transaction scope and uses getDomainErrorStatusCode to map domain errors to HTTP status codes

Before:

await db.transaction(async (tx) => {
  const result = await heatService.completeHeat(heatId, new Date());
  if (result.isErr()) {
    const status = getDomainErrorStatusCode(result.error);
    throw Object.assign(result.error, { _statusCode: status }); // ❌ Middleware ignores _statusCode
  }
});

After:

const txResult = await withResultTransaction(db, async (tx) => {
  return heatService.completeHeat(heatId, new Date());
});

if (txResult.isErr()) {
  const status = getDomainErrorStatusCode(txResult.error); // ✅ Explicit status mapping
  return createErrorResponse(txResult.error.message, status);
}

The implementation ensures transaction rollback on domain errors while preserving typed error information for proper HTTP status code mapping.

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