feat: Create dev container that contains all necesary tools and setup

[LazyGeniusMan]

What is the proposed feature?

Add dev container either features or templates that includes all tools and apply all setup necessary for development, testing, building, and distributing packages for all programming language supported by alef with configurable version of each programming language.

Why would this be a good addition?

It would make development, testing, building, and distributing packages easier. Developer can just spin up dev container to use alef. It can also be used in CI using devcontainers/ci

[Goldziher]

Thanks for the suggestion! A dev container that bundles all 11 language toolchains would be a welcome contribution.

A few notes for anyone picking this up:

• We already have task setup (via Taskfile.yaml) as the primary setup path — the dev container should complement this, not replace it. Ideally task setup runs inside the container as well.
• AI coding agents (Claude Code, Codex, etc.) typically run on the host or in their own sandboxes rather than attaching to dev containers, so this would primarily benefit human IDE workflows and potentially CI via devcontainers/ci.
• The polyrepo structure means the container needs to work from any subrepo root, not just the alef repo itself.

If you'd like to put together a PR, happy to review it.