chore: repin toolchain and fix asset setup on fresh machines

[aalvaropc]

What changed

• Repin .tool-versions to erlang 27.1.2 and nodejs 22.23.2 (latest Node 22 LTS patch), keeping elixir 1.17.3-otp-27.
• Align the Dockerfile builder image (hexpm/elixir:1.17.3-erlang-27.1.2-...) and CI OTP_VERSION with the same Erlang patch release.
• Add npm ci to the assets.setup mix alias so mix setup installs the JS dependencies (CodeMirror, Chart.js, SortableJS) needed by assets.build.
• Remove assets/tsconfig.json, an orphan config with no TypeScript sources in the project.

Why

The exact pins erlang 27.1 and nodejs 22.20.0 are no longer installable via asdf, so mix did not even run on a freshly provisioned machine. While reviving the project, make setup also failed on a fresh clone because nothing ever ran npm ci locally (only the Dockerfile did), breaking esbuild bundling with unresolved @codemirror/* imports. This PR makes local, CI, and release builds converge on one toolchain and makes make setup work end to end from a clean checkout.

How to test

asdf install        # picks up the new pins
make setup          # Docker DBs + deps + migrations + assets, from clean
mix precommit       # compile --warnings-as-errors + format + credo --strict + tests
make test.integration
docker build -t onesqlx:test .

All green locally: 638 tests + 10 properties (0 failures), integration suite against both Postgres containers, and the production image builds successfully.