Fix broken [nextPage] links and remove references to missing pages

[emirongrr]

Updating the Clave Docs

Summary

This PR fixes several issues with [nextPage] links throughout the documentation:

• Corrected malformed slugs such as "zkemail-recovery-technical" that were preventing navigation.
• Updated [nextPage] references pointing to .mdx files that do not exist.

Why?

Broken navigation links cause frustration and degrade the overall experience. These fixes improve the reliability of the docs by ensuring a smooth navigation flow across all pages.

Let me know if you'd prefer to redirect removed pages elsewhere or need additional cleanup.

Additional Fixes

• Fixed a broken link to the contribution guide which previously pointed to getclave.io
  Updated to https://docs.getclave.com/en/how-to-contribute-to-clave for correctness.

Checklist

• I am adding a new language
• I am updating an existing language
• I have read the contribution guidelines and followed the rules accordingly

Locale details

• Language names: English, Turkish

[emirongrr]

mistakenly updated the Turkish version incorrectly