Update README files with links to v1.5.0 release notes

- Add links to comprehensive release notes in both languages
- Update guide file references to correct .codepress.md extensions
- Complete v1.5.0 release documentation

CodePress CMS v1.5.0 is now fully documented and ready for release.

README.md

@@ -232,8 +232,9 @@ Hoofd CMS class die alle content management functionaliteit beheert.
 
 ## 📖 Documentatie
 
-- **[Handleiding (NL)](guide/nl.md)** - Gedetailleerde handleiding
-- **[Handleiding (EN)](guide/en.md)** - English documentation
+- **[Handleiding (NL)](guide/nl.codepress.md)** - Gedetailleerde handleiding
+- **[Handleiding (EN)](guide/en.codepress.md)** - English documentation
+- **[Release Notes v1.5.0](RELEASE-NOTES-v1.5.0.md)** - Uitgebreide release informatie
 - **[AGENTS.md](AGENTS.md)** - Ontwikkelaar instructies
 
 ## 🤝 Bijdragen