chore: Add playwright test artifacts to .gitignore

- playwright-report/ directory
- playwright-report.json file
- test-results/ directory

These are generated test artifacts and should not be committed to the repository.

Author: scttfrdmn

.gitignore

@@ -67,3 +67,8 @@ daemon_debug.log
 # MkDocs
 site/
 .cache/
+
+# Playwright test artifacts
+cmd/prism-gui/frontend/playwright-report/
+cmd/prism-gui/frontend/playwright-report.json
+cmd/prism-gui/frontend/test-results/