[grade=B] DC-071: Error tracking integration framework (Sentry-compatible)

Opt-in error tracking that forwards uncaught errors to Sentry/Bugsnag-style
services when ERROR_TRACKING_DSN env var is set. Without DSN, disabled.

Features:
- Sentry envelope format for wire compatibility
- Express error middleware (drop-in after routes)
- capture() + captureMessage() + flush()
- Non-blocking — tracking errors never crash the app
- 5s timeout on network sends
- Includes hostname, node version, memory, uptime, request context

10 tests, 1633 total pass.

dashcaddy-api/__tests__/error-tracker.test.js

@@ -0,0 +1,91 @@
+/**
+ * DC-071: Error tracker tests
+ */
+const errorTracker = require('../src/utilities/error-tracker');
+
+describe('DC-071: Error Tracker', () => {
+  beforeEach(() => {
+    // Reset to clean state
+    errorTracker.dsn = null;
+    errorTracker.enabled = false;
+  });
+
+  describe('init()', () => {
+    it('is disabled without DSN', () => {
+      const enabled = errorTracker.init({});
+      expect(enabled).toBe(false);
+      expect(errorTracker.enabled).toBe(false);
+    });
+
+    it('enables with DSN', () => {
+      const enabled = errorTracker.init({
+        dsn: 'https://abc123@sentry.io/123',
+        release: '1.15.0',
+      });
+      expect(enabled).toBe(true);
+      expect(errorTracker.enabled).toBe(true);
+      expect(errorTracker.release).toBe('1.15.0');
+    });
+
+    it('reads DSN from env', () => {
+      process.env.ERROR_TRACKING_DSN = 'https://key@sentry.io/456';
+      const enabled = errorTracker.init({});
+      expect(enabled).toBe(true);
+      delete process.env.ERROR_TRACKING_DSN;
+    });
+  });
+
+  describe('capture()', () => {
+    it('returns undefined when disabled', () => {
+      const result = errorTracker.capture(new Error('test'));
+      expect(result).toBeUndefined();
+    });
+
+    it('returns event ID when enabled', () => {
+      errorTracker.init({ dsn: 'https://key@sentry.io/123' });
+      const eventId = errorTracker.capture(new Error('test'));
+      expect(eventId).toBeTruthy();
+      expect(typeof eventId).toBe('string');
+    });
+
+    it('handles null error gracefully', () => {
+      errorTracker.init({ dsn: 'https://key@sentry.io/123' });
+      const result = errorTracker.capture(null);
+      expect(result).toBeUndefined();
+    });
+  });
+
+  describe('captureMessage()', () => {
+    it('returns undefined when disabled', () => {
+      const result = errorTracker.captureMessage('test');
+      expect(result).toBeUndefined();
+    });
+
+    it('returns event ID when enabled', () => {
+      errorTracker.init({ dsn: 'https://key@sentry.io/123' });
+      const eventId = errorTracker.captureMessage('test info', 'info');
+      expect(eventId).toBeTruthy();
+    });
+  });
+
+  describe('middleware()', () => {
+    it('calls next(err) after capturing', () => {
+      errorTracker.init({ dsn: 'https://key@sentry.io/123' });
+      const middleware = errorTracker.middleware();
+      const err = new Error('middleware test');
+      const req = { url: '/test', method: 'GET', headers: {}, path: '/test' };
+      const res = {};
+      let nextCalled = false;
+      let nextArg = null;
+      middleware(err, req, res, (e) => { nextCalled = true; nextArg = e; });
+      expect(nextCalled).toBe(true);
+      expect(nextArg).toBe(err);
+    });
+  });
+
+  describe('flush()', () => {
+    it('resolves without error', async () => {
+      await expect(errorTracker.flush(100)).resolves.toBeUndefined();
+    });
+  });
+});