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/Dockerfile

@@ -0,0 +1,50 @@
+FROM cloudron/base:5.0.0
+
+# Metadata labels
+LABEL org.opencontainers.image.title="Jenkins CI/CD"
+LABEL org.opencontainers.image.description="Cloudron package for Jenkins CI/CD Platform"
+LABEL org.opencontainers.image.source="https://github.com/jenkinsci/jenkins"
+
+# Install Java and Jenkins dependencies
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    openjdk-17-jdk \
+    curl \
+    ca-certificates \
+    git \
+    && rm -rf /var/lib/apt/lists/*
+
+# Set Java environment
+ENV JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
+ENV PATH=$JAVA_HOME/bin:$PATH
+
+# Create Jenkins directories
+RUN mkdir -p /app/data/jenkins_home && \
+    mkdir -p /app/data/plugins && \
+    mkdir -p /app/pkg && \
+    chown -R cloudron:cloudron /app/data
+
+# Download and install Jenkins WAR file
+ARG JENKINS_VERSION=2.450
+RUN cd /tmp && \
+    curl -fsSL "https://get.jenkins.io/war/${JENKINS_VERSION}/jenkins.war" -o jenkins.war && \
+    mv jenkins.war /app/pkg/jenkins.war && \
+    chown cloudron:cloudron /app/pkg/jenkins.war
+
+# Copy startup script
+COPY start.sh /app/pkg/start.sh
+RUN chmod +x /app/pkg/start.sh && chown cloudron:cloudron /app/pkg/start.sh
+
+USER cloudron
+
+# Expose Jenkins port
+EXPOSE 8080
+
+# Jenkins environment variables
+ENV JENKINS_HOME=/app/data/jenkins_home \
+    JENKINS_OPTS="--httpPort=8080 --httpListenAddress=0.0.0.0" \
+    APP_PORT=8080
+
+HEALTHCHECK --interval=30s --timeout=10s --start-period=60s --retries=3 \
+  CMD curl -fsS http://127.0.0.1:${APP_PORT}/login || exit 1
+
+CMD ["/app/pkg/start.sh"]