Add jest test suite, extract pure utils module, fix cron-parser v5 API

- Extract validateWebhookUrl, applyParams, evalCondition, calculateNextRun
  to lib/utils.js so they can be tested without DB connection
- Fix cron-parser v5 API: parseExpression → CronExpressionParser.parse
- Add 31 jest tests covering all four utility functions
- Add test.yml CI workflow running jest on every push/PR
- Add jest devDependency

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -3,7 +3,7 @@
   "version": "1.0.0",
   "main": "index.js",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "jest"
   },
   "keywords": [],
   "author": "",
@@ -18,6 +18,7 @@
     "ws": "^8.18.3"
   },
   "devDependencies": {
-    "eslint": "^8.57.1"
+    "eslint": "^8.57.1",
+    "jest": "^29.7.0"
   }
 }