Add base BugBot review rules scaffold

[yucetin]

Summary

• Adds .cursor/BUGBOT.md with starter code review rules tailored to this repo's tech stack.
• These are base scaffolds — repo owners should review and customise the rules for their specific needs.
• BugBot will use these rules in addition to the org-wide team rules when reviewing PRs.

What is this?

BugBot is Cursor's AI code reviewer. It reads .cursor/BUGBOT.md files to enforce repo-specific review standards. See the BugBot Developer Handbook for details.

Next steps

• Review the generated rules — remove any that don't apply, add repo-specific ones
• Consider adding nested .cursor/BUGBOT.md files for distinct modules if needed

[linear]

DX-866 Bugbot repo only base scaffold rules