CC-2081: Update Elixir to 1.19

[andy1li]

CC-2081: Update Elixir to 1.19

---

Note

Updates Elixir to 1.19 across configs and adds a new 1.19 Dockerfile.

• Build/Runtime:
  • Version bump: Update buildpack from elixir-1.18 to elixir-1.19 in:
    • compiled_starters/elixir/codecrafters.yml
    • solutions/elixir/01-jm1/code/codecrafters.yml
    • solutions/elixir/02-rg2/code/codecrafters.yml
  • Docker: Add dockerfiles/elixir-1.19.Dockerfile (based on elixir:1.19.4-alpine) with Hex/Rebar setup, deps install/compile, and cache of _build and deps.

^{Written by Cursor Bugbot for commit daeb41b. This will update automatically on new commits. Configure here.}

[linear]

CC-2081 Upgrade Elixir to 1.19