Initial commit: HC900 Crawler

Honeywell HC900을 Modbus TCP로 직접 폴링 → gRPC → C# 크롤러 → PostgreSQL.
기존 Experion OPC UA 데이터 경로를 HC900 직접 통신으로 대체.

- industrial-comm/cpp: C++ Modbus 게이트웨이 (gRPC 서버)
- src: C# .NET 8 ASP.NET Core 크롤러 + 웹 UI (3-Layer)
- mcp-server: Python FastMCP (RAG/NL2SQL/P&ID)
- 다중 컨트롤러(N-Controller) 지원

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

industrial-comm/cpp/include/itransport.hpp

@@ -0,0 +1,47 @@
+// ITransport 인터페이스 (🔥 최종본)
+// itransport.hpp
+
+
+#pragma once
+
+#include <cstdint>
+#include <vector>
+#include "transport_error.hpp"
+
+// transport 상태관리
+enum class TransportState {
+    Disconnected,
+    Connecting,
+    Connected,
+    Reconnecting,
+    Fault,
+};
+class ITransport {
+public:
+    virtual ~ITransport() = default;
+
+    // connection
+    virtual bool connect(const char* host, std::uint16_t port) = 0;
+    virtual void disconnect() = 0;
+    virtual bool is_connected() const = 0;
+
+    // state & error handling
+    virtual TransportState state() const = 0;
+    virtual TransportError last_error() const = 0;
+
+    // io policy
+    virtual bool can_io() const = 0;   // ⭐ 추가 (권장)
+    
+    // watchdog / reconnect / state machine
+    virtual void poll() = 0;
+    virtual void reset() = 0;   // ⭐ 추가
+
+    // register access
+    virtual bool read_registers(std::uint16_t addr,
+                                std::uint16_t count,
+                                std::vector<std::uint16_t>& out) = 0;
+
+    virtual bool write_registers(std::uint16_t addr,
+                                 const std::vector<std::uint16_t>& values) = 0;
+
+};