feat: add Karate UI e2e tests with data-e2e selectors (#124)
- Add e2e/ui/ as peer project to e2e/api/ (own pom.xml, runner, config)
- 5 critical UI journeys: upload, delete, analysis, batch-progress, rechunk
- 4 local-only tests: sidebar, i18n, error-states, pipeline-options
- 1 full happy path workflow covering all modes
- Add data-e2e attributes on all tested Vue components (decoupled from CSS)
- Add CONVENTIONS.md with 7 golden rules for writing Karate UI tests
- Update CI with dedicated e2e-ui job (Chrome headless, --no-sandbox)
- Update docs/contributing.md with UI test instructions
Closes #124
fdbab2f49e