Run BDD (behave) tests in CI #641

Summary

BDD tests using behave currently only run locally via run_bdd.sh. They should be included in CI to catch regressions automatically.

Current state

• Feature files live in tests/features/
• Step definitions in tests/features/steps/
• Environment setup in tests/features/environment.py
• Run locally with: uv run behave tests/features --capture

Requested action

Add a GitHub Actions job (or step in the existing tests.yml workflow) that:

1. Sets up PostgreSQL + PostGIS service container (same as pytest job)
2. Runs uv run behave tests/features --capture
3. Reports pass/fail status on the PR

Consider running BDD tests as a separate job so they don't block the unit/integration test results, and can be tagged (e.g. @backend, @migration) to run subsets.