Implement MySQL data container support and add test suites across PHP, Node.js, and Python

[ameliaknowscode]

Summary

• Implement full data container handling in Node.js and Python, mirroring the existing PHP implementation. Both CLIs now correctly build and run relational (mysql, mariadb, postgres) and non-relational (mongodb, neo4j) database containers with the correct environment variables, port defaults, and optional volume mounts.
• Fix three bugs in Node.js and Python CLIs discovered during smoke testing:
  • .env lookup now checks the project root first with build/ as a fallback, consistent with the PHP CLI
  • Volume mount env var names corrected to APP_HOST_VOLUME_PATH / APP_CONTAINER_VOLUME_PATH
  • App image build now passes DATA_REL_TYPE and DATA_NONREL_TYPE as build args, so conditional driver/client installation in Dockerfiles (e.g. default-mysql-client, pdo_mysql, pymysql) fires correctly
• Fix default port bug in PHP CLI: runDataContainer was hardcoded to port 5432 even when MySQL was selected; now defaults to 3306 for mysql/mariadb
• Add missing volume mount support for data containers in PHP CLI (DATA_REL_HOST_VOLUME_PATH / DATA_REL_CONTAINER_VOLUME_PATH were documented in .env.example but never wired up)
• Fix import typo in nodejs/commands/build.js (fimport → import)
• Add test suites for all three implementations: PHPUnit (17 tests), Node.js node:test (24 tests), pytest (26 tests) — covering env var correctness, Dockerfile selection, port defaults, and volume configuration

Test plan

• PHP unit tests: php vendor/bin/phpunit — 17/17 passing
• Node.js unit tests: npm test — 24/24 passing
• Python unit tests: python -m pytest python/tests/ — 26/26 passing
• PHP + MySQL smoke test: php bin/dapp-bk build against a Laravel 12 app — containers up, DB reachable
• Node.js + MySQL smoke test: node nodejs/bin/dapp-bk-node.js build — app container serving, /health/db returns MySQL connection OK
• Python + MySQL smoke test: python -m hig_docker_build_kit.cli build — app container serving, /health/db returns MySQL connection OK

🤖 Generated with Claude Code

[ameliaknowscode]

This is an overview of what existed already and what I added in this PR:

Language	Relational	Non-Relational
PHP	✅ Implemented + tested	✅ Implemented, ❌ not unit tested
Node.js	✅ Implemented + tested	✅ Implemented + tested
Python	✅ Implemented + tested	✅ Implemented + tested

The Non-relational tests are only the automated tests, I did not create any test projects to test manually. But MySQL in PHP, Node.js, and Python I did! I also tested with one of the Laravel 12 apps I built, it worked great!