Fix packaging guide URL in CONTRIBUTING.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: MattDHill

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 ## Building and Development
 
-See the [StartOS Packaging Guide](https://docs.start9.com/packaging-guide/) for complete environment setup and build instructions.
+See the [StartOS Packaging Guide](https://docs.start9.com/packaging/) for complete environment setup and build instructions.
 
 ### Quick Start