Synchronize the fixes from #1936, #1824, and #1961 across translated editions and normalize C# and Dart formatting. Move Java CI to Ubuntu 24.04 so its Java 11/17 checks can run.
Replace the exercise pages' Python-only snippets with source-backed implementations for the 13 visible programming languages, and localize reader-facing comments by site language. Zig remains out of scope.
Approval bypass: repository protection requires one approval but does not enforce it for administrators. All 68 completed checks succeeded; four non-required Java jobs remained queued on the existing ubuntu-20.04 workflow, with no failed checks.
