test(geschichten): cover multi-person AND filter end-to-end

Adds a Playwright flow that picks two persons through the typeahead,
asserts both ?personId= params end up in the URL with two chips on
screen, then removes the first chip and verifies only the second
person id remains.

Also extends .prettierignore so a stale root-owned test-results
directory left over from running tests inside Docker doesn't break
the pre-commit lint hook.

frontend/.prettierignore

@@ -23,5 +23,6 @@ bun.lockb
 
 # Test artifacts
 /test-results/
+/test-results.locked/
 /e2e/.auth/
 /coverage/