✅ Add frontend/playwright/.auth to .dockerignore to fix e2e tests run locally

[YuriiMotov]

Description

Currently if you run playwright tests locally, they will fail because Playwright updates file inside frontend/playwright/.auth and it triggers backend service reload during the tests.

To reproduce:

docker compose watch backend db mailcatcher

# In another terminal
cd frontend
bunx playwright test

See several random tests failing on each run.

To fix this we need to ignore this path by adding it to .dockerignore

AI Disclaimer

Used Claude Code (Opus 5) to investigate and fix the issue. Reviewed and verified manually

Checklist

• This PR links to a GitHub Discussion for the proposed code change.
• I added tests for the change.
• The new or updated tests fail on the main branch and pass on this PR.
• Coverage stays at 100%.
• The documentation explains the change if needed.