Update repository URLs to karva-dev/seal

[MatthewMckee4]

Summary

• Updates all repository URLs, badge links, and references from MatthewMckee4/seal to karva-dev/seal following the repository transfer
• Updates documentation site URL from matthewmckee4.github.io/seal to karva-dev.github.io/seal
• Updates Codecov slug, Cargo.toml metadata, issue templates, and CI workflow

Test plan

• Verify links in README render correctly on GitHub
• Verify Codecov badge resolves to the correct project
• Verify CI workflow uploads coverage to the correct Codecov slug

[codecov]

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