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>

proto/modbus_gateway.proto

@@ -0,0 +1,98 @@
+syntax = "proto3";
+
+package hc900;
+
+import "google/protobuf/timestamp.proto";
+
+option csharp_namespace = "Hc900.Gateway";
+
+// ─── Data types ───
+
+message TagValue {
+  string tag_name = 1;
+  oneof value {
+    float  float32_val = 2;
+    uint32 uint16_val  = 3;
+  }
+  uint32 quality      = 4;  // 192=good, 0=bad
+  google.protobuf.Timestamp timestamp = 5;
+}
+
+message TagMetadata {
+  string tag_name   = 1;
+  uint32 address    = 2;
+  uint32 count      = 3;  // register count (1 for uint16, 2 for float32)
+  string type       = 4;  // "float32" or "uint16"
+  string access     = 5;  // "R" or "RW"
+  string description = 6;
+  string eu          = 7;  // engineering unit
+}
+
+// ─── Read ───
+
+message ReadTagsRequest {
+  repeated string tag_names = 1;  // empty means "all cached"
+}
+
+message ReadTagsResponse {
+  repeated TagValue values = 1;
+  bool from_cache = 2;
+}
+
+// ─── Write ───
+
+message WriteTagRequest {
+  string tag_name = 1;
+  double value    = 2;     // always sent as double; gateway casts to float32 or uint16
+}
+
+message WriteTagResponse {
+  bool   success = 1;
+  string error   = 2;
+}
+
+// ─── Stream (real-time) ───
+
+message StreamTagsRequest {
+  int32  interval_ms = 1;  // 0 = push on every poll
+  repeated string tag_names = 2;  // empty = all
+}
+
+// ─── Metadata ───
+
+message ListTagsRequest {
+  string filter = 1;  // tag name prefix match, empty = all
+  int32  limit  = 2;  // 0 = unlimited
+}
+
+message ListTagsResponse {
+  repeated TagMetadata tags = 1;
+}
+
+// ─── Health ───
+
+message HealthCheckRequest {}
+
+message HealthCheckResponse {
+  enum ServingStatus {
+    UNKNOWN = 0;
+    SERVING = 1;
+    NOT_SERVING = 2;
+  }
+  ServingStatus status      = 1;
+  double        uptime_sec  = 2;
+  uint64        poll_count  = 3;
+  double        last_poll_ms = 4;  // duration of last full poll in ms
+  string        controller_ip = 5;
+  uint32        active_tags   = 6;
+}
+
+// ─── Service ───
+
+service ModbusGateway {
+  rpc ReadTags(ReadTagsRequest) returns (ReadTagsResponse);
+  rpc WriteTag(WriteTagRequest) returns (WriteTagResponse);
+  rpc StreamTags(StreamTagsRequest) returns (stream TagValue);
+  rpc ListTags(ListTagsRequest) returns (ListTagsResponse);
+  rpc HealthCheck(HealthCheckRequest) returns (HealthCheckResponse);
+}