Bump MCPG to v0.3.1 and AWF firewall to v0.25.29

[lpcox]

Summary

Bump default component versions:

Component	Current	Target
MCP Gateway (gh-aw-mcpg)	v0.3.0	v0.3.1
AWF Firewall (gh-aw-firewall)	v0.25.28	v0.25.29

File to Modify

pkg/constants/version_constants.go:

const DefaultFirewallVersion Version = "v0.25.29"    // was v0.25.28
const DefaultMCPGatewayVersion Version = "v0.3.1"    // was v0.3.0

Post-Change Steps

1. make build — rebuild binary with new defaults
2. make recompile — regenerate all lock files with updated versions
3. make agent-finish — full validation (build + test + fmt + lint)
4. Verify lock files reference the new versions:

   grep -r "gh-aw-mcpg:v" .github/workflows/*.lock.yml | head -5
   grep -r "firewall.*v0\." .github/workflows/*.lock.yml | head -5