MAESTRO: Add comprehensive hook-categories.json for intelligent code sample generation

Created hook category mapping file with:
- 116 pattern definitions for hook name matching (field_output, before_, after_, calendar_, export_, etc.)
- 30 product context descriptions for all GravityKit products
- 28 type examples for PHP type inference in code samples
- 59 category descriptions for documentation

This file enables the code sample generator to produce contextually appropriate examples based on hook naming patterns and product context.

Author: zackkatz