Fix jsonrpc router default feature

[yeoleobun]

Summary

• remove addon-jsonrpc-router from default features because the repository only contains a symlink to private addon source
• move SSE-related AMI imports into the commerce-only handler where they are used

Root cause

CI enables default features while building with --features cross. The default feature set included addon-jsonrpc-router, but src/addons/jsonrpc_router is a symlink to ../../../rustpbx-addons/jsonrpc_router, so GitHub Actions cannot resolve src/addons/jsonrpc_router/mod.rs.

Validation

• cargo check
• cargo check --features cross