Play Framework

chore: drop pre-Gradle CI + .gitignore stragglers (PF-90)

- build-test.yml: remove the actions/setup-python@v6 step. Nothing
  in the framework or its build invokes Python anymore (PF-90 deleted
  framework/pym/), so the install was just adding ~15s per matrix run
  for nothing.
- codeql.yml: drop 'python' from the CodeQL language matrix. Same
  reason — there's no first-party Python code to scan.
- .gitignore: strip 58 lines of dead samples-and-tests/* ignores.
  The directory was deleted long ago; the ignore patterns were
  silently accumulating cruft and were a frequent grep false-positive.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>