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/package.json

@@ -8,7 +8,9 @@
     "start": "node dist/index.js",
     "dev": "nodemon --watch src --ext ts --exec ts-node src/index.ts",
     "lint": "eslint src",
-    "migrate": "ts-node src/db/migrate.ts"
+    "migrate": "ts-node src/db/migrate.ts",
+    "test": "jest",
+    "test:coverage": "jest --coverage"
   },
   "dependencies": {
     "@influxdata/influxdb-client": "^1.33.2",
@@ -35,6 +37,7 @@
     "@types/compression": "^1.7.5",
     "@types/cors": "^2.8.17",
     "@types/express": "^4.17.21",
+    "@types/jest": "^29.5.14",
     "@types/jsonwebtoken": "^9.0.5",
     "@types/morgan": "^1.9.9",
     "@types/node": "^20.10.5",
@@ -43,7 +46,9 @@
     "@types/ssh2": "^1.11.17",
     "eslint": "^9.39.4",
     "eslint-plugin-security": "^4.0.0",
+    "jest": "^29.7.0",
     "nodemon": "^3.0.2",
+    "ts-jest": "^29.4.9",
     "ts-node": "^10.9.2",
     "typescript": "^5.3.3",
     "typescript-eslint": "^8.58.2"