chore: repo professionalization — templates, security, contributing, codeowners

[Layellie]

Summary

Brings the GitHub-side metadata up to a reasonable baseline for a public utility that runs as Administrator and calls into ntdll. None of this changes app runtime behavior — .github/ and root metadata only. CI will not run for this PR (paths-ignore: **.md and .github/dependabot.yml); the new templates take effect on merge.

What's in

• Issue templates (bug_report.yml, feature_request.yml) with required fields. Bug report demands app version + Windows build + 30 lines of log.txt; feature request enforces "problem before solution" framing.
• config.yml disables blank issues and routes security reports to the SECURITY policy via the contact-links pane.
• PR template mirrors the project's actual review checklist (warnaserror Release build, layout-shift smoke for Views/Cards/*.xaml changes, Strings.tr-TR.xaml parity for English string additions, native-handle cleanup verification).
• SECURITY.md routes reports to GitHub's private advisory flow (with an email fallback). Documents the "latest release only" support policy explicitly — the v2.0.8/9/10 pre-release re-labelings now have a written rationale.
• CONTRIBUTING.md captures the conventions already in CLAUDE.md: P/Invoke isolated in NativeMethods.cs, strict MVVM in views, two-language string parity, one-logical-change-per-PR.
• CODEOWNERS routes every path to @Layellie for review.

Related repo settings already applied via gh repo edit

• deleteBranchOnMerge = true (merged branches auto-delete)
• Topics: removed bogus form, added wpf, dotnet, dotnet10
• homepageUrl → Releases page

Test plan

• All files are non-executing metadata — no behavior change.
• After merge: open a fresh issue → templates render with required fields.
• After merge: open a fresh PR → template body prefills.
• After merge: visit Security tab → policy resolves.

🤖 Generated with Claude Code