Add Jest unit test infrastructure and initial test suite

Sets up Jest + ts-jest for the backend and adds 47 tests across 5
suites covering crypto utilities, OUI vendor lookup, auth middleware,
AlertService dispatch/cooldown logic, and DeviceCollector uptime parsing.

backend/src/services/mikrotik/__tests__/DeviceCollector.test.ts

@@ -0,0 +1,64 @@
+// Mock external deps before importing DeviceCollector
+jest.mock('../../../utils/crypto', () => ({ decrypt: (s: string) => s }));
+jest.mock('../RouterOSClient');
+jest.mock('../../../config/database');
+jest.mock('../../../config/influxdb');
+jest.mock('../../../utils/oui');
+jest.mock('../../../utils/serverArp');
+
+import { DeviceCollector, DeviceRow } from '../DeviceCollector';
+
+const testDevice: DeviceRow = {
+  id: 1,
+  name: 'test-router',
+  ip_address: '192.168.1.1',
+  api_port: 8728,
+  api_username: 'admin',
+  api_password_encrypted: 'plaintext-password',
+  device_type: 'router',
+  status: 'online',
+};
+
+// ── parseUptime ───────────────────────────────────────────────────────────────
+
+describe('parseUptime', () => {
+  let collector: DeviceCollector;
+
+  beforeEach(() => {
+    collector = new DeviceCollector(testDevice);
+  });
+
+  function parse(uptime: string): number {
+    // Access private method for unit testing
+    return (collector as unknown as Record<string, (s: string) => number>).parseUptime(uptime);
+  }
+
+  it('parses a full uptime string (1w2d3h4m5s)', () => {
+    // 1w=604800, 2d=172800, 3h=10800, 4m=240, 5s=5 → 788645
+    expect(parse('1w2d3h4m5s')).toBe(788645);
+  });
+
+  it('parses weeks only', () => {
+    expect(parse('2w')).toBe(2 * 604800);
+  });
+
+  it('parses days only', () => {
+    expect(parse('3d')).toBe(3 * 86400);
+  });
+
+  it('parses hours and minutes', () => {
+    expect(parse('5h30m')).toBe(5 * 3600 + 30 * 60);
+  });
+
+  it('parses seconds only', () => {
+    expect(parse('45s')).toBe(45);
+  });
+
+  it('returns 0 for an empty string', () => {
+    expect(parse('')).toBe(0);
+  });
+
+  it('returns 0 for zero-second uptime (0s)', () => {
+    expect(parse('0s')).toBe(0);
+  });
+});