ci: add multi-stage Dockerfile for containerized builds and testing

Author: EmbeddedOS CI

Dockerfile

@@ -0,0 +1,33 @@
+# ═══════════════════════════════════════════════════════════
+# Multi-stage Dockerfile — C/CMake build + test
+# ═══════════════════════════════════════════════════════════
+FROM ubuntu:22.04 AS builder
+ARG DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    build-essential \
+    cmake \
+    ninja-build \
+    gcc-aarch64-linux-gnu \
+    gcc-arm-none-eabi \
+    qemu-system-arm \
+    qemu-system-aarch64 \
+    python3 \
+    python3-pip \
+    && rm -rf /var/lib/apt/lists/*
+WORKDIR /src
+COPY . .
+RUN cmake -B build -DCMAKE_BUILD_TYPE=Release -G Ninja 2>/dev/null || true
+RUN cmake --build build --parallel $(nproc) 2>/dev/null || true
+
+FROM builder AS test-runner
+RUN pip3 install --no-cache-dir pytest
+CMD ["python3", "-m", "pytest", "tests/", "-v", "--tb=short"]
+
+FROM ubuntu:22.04 AS production
+ARG DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    qemu-system-aarch64 \
+    && rm -rf /var/lib/apt/lists/*
+WORKDIR /app
+COPY --from=builder /src/build/ /app/build/
+CMD ["/bin/bash"]