feature: add GET /version returning app version for coding-agent smoke

## Problem
Need a tiny version endpoint to prove Copilot coding agent auto-assign on the bcgov Tier 2 pattern repo.

## Outcome
`GET /version` returns HTTP 200 with JSON like `{"version":"0.1.0"}`.

## Spec reference
spec/features/example-happy-path.feature

## Acceptance criteria
Given the Node service under `src/`
When a client calls GET /version
Then the response status is 200
And the body is JSON including a version string

## Constraints
- Keep the change small under `src/`
- Open a **draft** pull request; do not merge
- Update `docs/pr-evidence.md`
- Follow AGENTS.md and the constitution