* findWebDir: CWD and project root checked before binary-adjacent path,
so dev always serves fresh web/build/ over stale bin/web/build/
* build-go: auto-copies web/build/ to bin/web/ before Go compile
* build-prod: same auto-copy for production builds
* Proper refresh of frontend static on every make build
- Emulator: add sip_gateway field to all scenarios (auto-trunk creation)
- Makefile: build-agent, build-siptest, emulate-*, siptest-* targets
- README: full documentation with agent section, production deployment
- Project structure update with all components
