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/transport_state.hpp

@@ -0,0 +1,9 @@
+#pragma once
+
+enum class TransportState {
+    Disconnected,
+    Connecting,
+    Connected,
+    Reconnecting,
+    Fault
+};