feat(jenkins): add Jenkins CI/CD Platform Cloudron package

- Complete Jenkins package with Java 17 and WAR file download
- Proper CloudronManifest.json with correct metadata
- Custom start.sh script with Jenkins configuration
- Health check endpoint configured for /login
- Follows KNELCloudron- naming convention
- Added comprehensive packaging shortlist with 56 applications prioritized by phase

CloudronPackages/Jenkins/CloudronManifest.json

@@ -0,0 +1,19 @@
+{
+  "manifestVersion": 2,
+  "id": "io.knel.jenkins",
+  "title": "Jenkins CI/CD",
+  "author": "KNEL",
+  "description": "Jenkins CI/CD Platform for automated builds, testing, and deployment",
+  "website": "https://jenkins.io",
+  "contactEmail": "admin@knownelement.com",
+  "version": "2.450.0",
+  "changelog": "Initial Cloudron package for Jenkins CI/CD Platform",
+  "healthCheckPath": "/login",
+  "httpPort": 8080,
+  "addons": {
+    "localstorage": {}
+  },
+  "tags": ["ci", "cd", "automation", "build", "deployment"],
+  "icon": "logo.png"
+}
+