Add cart pin synchronization to prevent metastability

[eric-humane]

Overview

This PR implements proper synchronization for cartridge pins and interface signals to prevent metastability issues when crossing clock domains. It adds a parameterized two-stage synchronizer module and introduces GBA PHI clock generation for cartridge operations.

Key Changes

• Add cart_pin_synchronizer.sv
  • reusable two-stage synchronization module with proper bitwise vector operations
• Implement synchronizers for all cartridge banks/pins with synthesis preservation attributes
• Add proper direction signal synchronization with break-before-make protection
• Generate PHI clock (~1.058 MHz) for cartridge timing
• Update signal paths to use synchronized inputs