Docker based Development Setup

[GALHP]

Summary

Containerized local dev setup (Docker Compose + make targets) so clonio-cli
builds/runs/tests without a host PHP toolchain, and makes the init IO-error
tests pass under the container's root user.

Stacked PR — base: main · 1st of 6 · Part of #164 (series overview).
Pure tooling, no runtime behavior — safe to merge or skip independently.

Motivation

Contributors otherwise need a matching PHP 8.x + extensions setup. A throwaway
container removes that friction and gives everyone the same composer test /
composer lint environment.

What's changed

• compose.yaml — one php service (wodby/php:8.5), repo bind-mounted at
  /var/www/html, php -v healthcheck.
• Makefile.dev.mk (+ hook in Makefile) — make up/down/restart/
  bash, make test (XDEBUG_MODE=coverage composer test), make check
  (composer lint && composer test:types).
• .env.example — APP_KEY + DEV_PHP_VERSION hint.
• tests/Feature/Commands/InitCommandTest.php — the two "cannot write .env"
  IO-error tests simulated a read-only disk with chmod, a no-op under root
  (the container), so they failed there; they now mock Storage::put() returning
  false — user-independent, same error path.

Testing

make up && make test — full suite green in the container.