Add HealthMonitor service for tracking system health status with
comprehensive state transition logic and thread-safe operations.
Includes 16 unit tests covering all functionality including concurrent
access scenarios.
Add optional Modbus hardware integration tests with 7 test cases for
real device testing. Tests are marked as ignored and can be run with
Ref: T034, T039, T040 (specs/001-modbus-relay-control/tasks.org)
Convert project from single backend to monorepo structure with separate
frontend (Vue 3 + TypeScript + Vite) and backend directories. Updates
all configuration files and build system to support both workspaces.
Ref: T007 (specs/001-modbus-relay-control)
