Update repository references from MatthewMckee4 to karva-dev

[MatthewMckee4]

Summary

• Update all repository URLs, slugs, and references from MatthewMckee4/action-format to karva-dev/action-format
• Update GitHub Pages site URL from matthewmckee4.github.io to karva-dev.github.io
• Files updated: Cargo.toml, README.md, zensical.toml, .github/workflows/ci.yml, .github/action-format.toml, .github/ISSUE_TEMPLATE/1_bug_report.yaml

Test plan

• Verify all links in README point to the correct repository
• Verify Codecov badge and slug resolve correctly
• Verify CI workflow runs successfully

[codecov]

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