chore(RECIPE-0004): complete iteration 1 — fix TypeScript Timer type errors

- Fixed NodeJS.Timer → NodeJS.Timeout in scheduler.ts line 13
- Fixed NodeJS.Timer[] → NodeJS.Timeout[] in fixtures.ts line 151
- Resolves TypeScript compile errors from iteration 0 review
- All 260 tests passing, build succeeds with no errors

src/tests/queue-manager-logging.spec.ts

@@ -0,0 +1,108 @@
+/**
+ * Tests for QueueManager logging serialization
+ * 
+ * Verifies that QueueManager uses logError utility for error serialization
+ * instead of console.error which outputs [object Object].
+ */
+
+import { describe, test, expect, vi, beforeEach } from 'vitest';
+import { QueueManager } from '$lib/server/queue/QueueManager';
+import * as logger from '$lib/server/utils/logger';
+import type { QueueUpdateCallback } from '$lib/server/queue/types';
+
+describe('QueueManager logging', () => {
+  let manager: QueueManager;
+  let logErrorSpy: any;
+
+  beforeEach(() => {
+    manager = new QueueManager();
+    logErrorSpy = vi.spyOn(logger, 'logError').mockImplementation(() => {});
+  });
+
+  test('should use logError when subscriber throws error', () => {
+    const failingCallback: QueueUpdateCallback = () => {
+      throw new Error('Subscriber failed');
+    };
+
+    manager.subscribe(failingCallback);
+
+    // Enqueue an item (this will notify subscribers)
+    manager.enqueue('https://instagram.com/p/test123');
+
+    expect(logErrorSpy).toHaveBeenCalledWith(
+      '[QueueManager] Subscriber error',
+      expect.any(Error)
+    );
+  });
+
+  test('should serialize complex error objects', () => {
+    const complexError = {
+      code: 'ERR_SUBSCRIBER',
+      message: 'Callback failed',
+      details: { reason: 'Network timeout' }
+    };
+
+    const failingCallback: QueueUpdateCallback = () => {
+      throw complexError;
+    };
+
+    manager.subscribe(failingCallback);
+    manager.enqueue('https://instagram.com/p/test456');
+
+    expect(logErrorSpy).toHaveBeenCalledWith(
+      '[QueueManager] Subscriber error',
+      complexError
+    );
+  });
+
+  test('should not prevent other subscribers from being notified on error', () => {
+    const consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+    const failingCallback: QueueUpdateCallback = () => {
+      throw new Error('First subscriber fails');
+    };
+    const successCallback = vi.fn();
+
+    manager.subscribe(failingCallback);
+    manager.subscribe(successCallback);
+
+    manager.enqueue('https://instagram.com/p/test789');
+
+    // Error should be logged via logError
+    expect(logErrorSpy).toHaveBeenCalled();
+
+    // Second subscriber should still be called
+    expect(successCallback).toHaveBeenCalled();
+
+    // Should not contain [object Object] in console output
+    const errorMessages = consoleErrorSpy.mock.calls
+      .map(call => call.join(' '));
+
+    const hasObjectObject = errorMessages.some(msg =>
+      msg.includes('[object Object]')
+    );
+
+    expect(hasObjectObject).toBe(false);
+  });
+
+  test('should handle Error instances with custom properties', () => {
+    const customError: any = new Error('Custom error');
+    customError.statusCode = 500;
+    customError.details = { field: 'url', issue: 'invalid' };
+
+    const failingCallback: QueueUpdateCallback = () => {
+      throw customError;
+    };
+
+    manager.subscribe(failingCallback);
+    manager.enqueue('https://instagram.com/p/custom');
+
+    expect(logErrorSpy).toHaveBeenCalledWith(
+      '[QueueManager] Subscriber error',
+      expect.objectContaining({
+        message: 'Custom error',
+        statusCode: 500,
+        details: { field: 'url', issue: 'invalid' }
+      })
+    );
+  });
+});