Fix outdated MathCAT project URLs

[k4its1t]

Summary

• point the crate repository, homepage, documentation, and README documentation link at the DAISY-owned locations
• update contributor instructions and historical issue references to use daisy/MathCAT
• retain links to the separately owned MathCATForPython, MathCATForC, and MathCATDemo projects
• leave the generated coverage HTML unchanged so it remains an accurate historical artifact

Validation

• cargo metadata --no-deps --format-version 1
• git diff --check
• verified the repository, documentation site, and representative issue URLs return HTTP 200
• audited non-generated tracked content for remaining references to the old MathCAT repository and documentation locations

AI assistance

Codex was used to audit the repository for stale URLs, apply the mechanical replacements, and run the validation described above. The final diff was reviewed to ensure related NSoiffer-owned projects were not changed.

Closes #719

[moritz-gross]

hi @k4its1t, thanks for your first contribution. all changes look good to me.
I'm surprised that so many unit tests have URLs in their comments that need to be changed, but that's what it is then.

@NSoiffer why does GitHub ask me to "aprove workflows to run"? Is this because the CI jobs for linting are too expensive to run automatically every time? Ideally, they should be run before every merge I assume?

[NSoiffer]

Changes look good.

@moritz-gross: apparently because it is a first time contribution. Here is what Gemini says:

GitHub requires workflow approval because the pull request is submitted by a first-time contributor to the repository.

GitHub Actions enforces this security policy by default on public repositories to prevent malicious actors from submitting pull requests that automatically execute untrusted code or abuse runner resources (such as crypto-mining or secret exfiltration).

A maintainer with write access must review the changes and click Approve workflows to run before the automated CI jobs can trigger. Once a contributor's pull request is merged or they are granted repository permissions, future workflow runs from them can trigger automatically depending on the repository's Actions settings.

[moritz-gross]

@NSoiffer ok sounds reasonable i think?!? so we will just keep it like this?