Adds a "Report a bug" / "Segnala un bug" button (6 languages) in
Help → Info that opens the repository issue tracker in the system
browser via TopLevel.Launcher (cross-platform: desktop + Android).
Adds .gitea/ISSUE_TEMPLATE/bug_report.md — Gitea-compatible markdown
template with pre-filled sections for version, platform, network,
repro steps, expected behavior, and logs.
