Adds localnet testing mode to gateway-probe for LP development:
- Add TestMode enum for different probe configurations
- Add --gateway-ip flag for direct gateway testing
- Implement two-hop WireGuard tunnel for localnet
- Add mock ecash support for testing without real credentials
- Add netstack Go bindings for userspace networking
- Restructure probe with mode and common modules
- Update README with localnet mode documentation
durch
65bd47f342