📦 build: Add devcontainer for local Kubernetes development

.devcontainer/Dockerfile

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+FROM ubuntu:24.04
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Install base packages
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    openssh-server \
+    passwd \
+    sudo \
+    curl \
+    wget \
+    git \
+    jq \
+    unzip \
+    ca-certificates \
+    gnupg \
+    lsb-release \
+    iptables \
+    iproute2 \
+    postgresql-client \
+    apt-transport-https \
+    software-properties-common \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Node.js 24
+RUN curl -fsSL https://deb.nodesource.com/setup_24.x | bash - \
+    && apt-get install -y --no-install-recommends nodejs \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Bun
+RUN curl -fsSL https://bun.sh/install | bash \
+    && mv /root/.bun/bin/bun /usr/local/bin/ \
+    && ln -s /usr/local/bin/bun /usr/local/bin/bunx
+
+# Install Docker
+RUN curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg \
+    && echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" > /etc/apt/sources.list.d/docker.list \
+    && apt-get update \
+    && apt-get install -y --no-install-recommends docker-ce docker-ce-cli containerd.io docker-compose-plugin \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install kubectl
+RUN curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/$(dpkg --print-architecture)/kubectl" \
+    && install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl \
+    && rm kubectl
+
+# Install Helm
+RUN curl -fsSL https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bash
+
+# Enable systemd
+RUN find /lib/systemd/system/sysinit.target.wants -mindepth 1 -not -name "systemd-tmpfiles-setup.service" -delete; \
+    find /lib/systemd/system/multi-user.target.wants -mindepth 1 -not -name "systemd-user-sessions.service" -delete; \
+    rm -f /etc/systemd/system/*.wants/*; \
+    rm -f /lib/systemd/system/local-fs.target.wants/*; \
+    rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
+    rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
+    rm -f /lib/systemd/system/basic.target.wants/*; \
+    rm -f /lib/systemd/system/anaconda.target.wants/*;
+
+# Create dev user with host UID/GID for seamless file permissions
+ARG HOST_UID=1000
+ARG HOST_GID=1000
+RUN userdel -r $(getent passwd ${HOST_UID} | cut -d: -f1) 2>/dev/null || true && \
+    groupdel $(getent group ${HOST_GID} | cut -d: -f1) 2>/dev/null || true && \
+    groupadd -g ${HOST_GID} dev && \
+    useradd -m -s /bin/bash -u ${HOST_UID} -g ${HOST_GID} dev && \
+    echo "dev:dev" | chpasswd && \
+    echo 'dev ALL=(ALL) NOPASSWD: ALL' > /etc/sudoers.d/dev && \
+    chmod 440 /etc/sudoers.d/dev && \
+    usermod -aG docker dev
+
+# Setup directories
+RUN mkdir -p /home/dev/.kube && chown -R dev:dev /home/dev
+
+WORKDIR /workspace
+
+VOLUME [ "/sys/fs/cgroup" ]
+CMD ["/usr/sbin/init"]