Fix better-sqlite3 architecture in Docker images - #1541

Summary

• Rebuild better-sqlite3 in a target-platform build stage for both the Debian and Alpine images.
• Copy the rebuilt application into the final runtime stage, keeping compiler toolchains out of the final images.
• Open an in-memory SQLite database during each platform build, so a wrong-architecture native addon fails the existing multi-arch build immediately.

Related to #653.

Root cause

.github/workflows/build-docker.yaml runs yarn prepare:docker on the x86_64 GitHub Actions runner before Docker Buildx starts. prepare:docker calls install:drivers:docker, which installs better-sqlite3 and creates:

docker/node_modules/better-sqlite3/build/Release/better_sqlite3.node

for x86_64.

Buildx subsequently builds linux/amd64, linux/arm64, and linux/arm/v7, but the Dockerfiles only copy that already-prepared directory. A COPY does not rebuild native addons, so the ARM images receive the x86-64 ELF.

Reproduction

On an ARM64 host:

docker pull --platform linux/arm64 dbgate/dbgate:7.2.5

docker run --rm \
  --platform linux/arm64 \
  --entrypoint node \
  dbgate/dbgate:7.2.5 \
  -e "const Database = require('better-sqlite3'); const db = new Database(':memory:'); db.close()"

This fails with ERR_DLOPEN_FAILED because the native addon has the wrong architecture.

The addon can also be inspected from the image:

docker create \
  --platform linux/arm64 \
  --name dbgate-arm64-inspect \
  dbgate/dbgate:7.2.5

docker cp \
  dbgate-arm64-inspect:/home/dbgate-docker/node_modules/better-sqlite3/build/Release/better_sqlite3.node \
  ./better_sqlite3.node

docker rm dbgate-arm64-inspect
file ./better_sqlite3.node

Before this change, file reports an x86-64 ELF even though the image platform is ARM64.