feat(jenkins): Add custom Dockerfile with Docker CLI and kubectl

apps/jenkins/Dockerfile

@@ -0,0 +1,41 @@
+FROM jenkins/jenkins:lts-jdk17
+
+USER root
+
+# Install Docker CLI
+RUN apt-get update && \
+    apt-get install -y \
+        ca-certificates \
+        curl \
+        gnupg \
+        lsb-release && \
+    mkdir -p /etc/apt/keyrings && \
+    curl -fsSL https://download.docker.com/linux/debian/gpg | gpg --dearmor -o /etc/apt/keyrings/docker.gpg && \
+    echo \
+      "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/debian \
+      $(lsb_release -cs) stable" | tee /etc/apt/sources.list.d/docker.list > /dev/null && \
+    apt-get update && \
+    apt-get install -y docker-ce-cli && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
+# Install kubectl
+RUN curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl" && \
+    chmod +x kubectl && \
+    mv kubectl /usr/local/bin/
+
+# Install git (if not already)
+RUN apt-get update && apt-get install -y git && rm -rf /var/lib/apt/lists/*
+
+USER jenkins
+
+# Pre-install useful plugins
+RUN jenkins-plugin-cli --plugins \
+    git \
+    docker-workflow \
+    pipeline-stage-view \
+    kubernetes \
+    configuration-as-code \
+    job-dsl \
+    workflow-aggregator \
+    gitea