fix: multi-platform Docker build for ARM devices

[fabrizio-monaco]

Summary

Fixes exec /entrypoint.sh: exec format error when deploying on ARM-based devices (e.g. Raspberry Pi) by enabling multi-platform Docker builds.

Changes

Multi-platform CI build (docker.yml)

• Added docker/setup-qemu-action for cross-platform emulation
• Added docker/setup-buildx-action to enable Docker Buildx
• Build now targets linux/amd64, linux/arm64, and linux/arm/v7

Multi-stage Dockerfile (Dockerfile)

• Builder stage: installs gcc, libffi-dev, libjpeg62-turbo-dev, zlib1g-dev to compile native dependencies (cffi, Pillow) from source on ARM architectures where no pre-built wheels are available
• Runtime stage: copies only the compiled packages — no compiler or dev headers in the final image, keeping it slim
• Added libjpeg62-turbo as runtime dependency for Pillow

Platforms supported

Architecture	Example devices
linux/amd64	Standard PCs, servers
linux/arm64	Raspberry Pi 4/5, Apple Silicon
linux/arm/v7	Raspberry Pi 2/3 (32-bit)

Closes #1

[itsDNNS]

Great contribution, thanks @fabrizio-monaco! 🎉

Multi-stage build approach is clean. Keeps the runtime image slim while handling native compilation for ARM. QEMU + Buildx setup looks solid.

One minor thing: I'll remove the fix/* branch trigger after merge since we don't use that pattern in our workflow. Everything else looks good to go.

Appreciate you jumping on this so quickly after the issue was opened!