Go: introduce clickhouse (#16996)

### Summary

Introduce Clickhouse for data statistics.

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

cmd/ragflow_server.go

@@ -27,6 +27,7 @@ import (
 	"ragflow/internal/agent/audio"
 	"ragflow/internal/agent/canvas"
 	agenttool "ragflow/internal/agent/tool"
+	"ragflow/internal/engine/clickhouse"
 	"ragflow/internal/handler"
 	ingestion "ragflow/internal/ingestion/service"
 	"ragflow/internal/mcp"
@@ -363,6 +364,12 @@ func main() {
 		common.Error("Failed to initialize message queue engine", err)
 	}
 
+	ctx := context.Background()
+	if err = clickhouse.Init(&config.Clickhouse, ctx); err != nil {
+		common.Error("Failed to initialize ClickHouse", err)
+	}
+	defer clickhouse.Close()
+
 	// Initialize server variables (runtime variables that can change during operation)
 	// This must be done after Cache is initialized
 	if err = server.InitVariables(redis.Get()); err != nil {