refactor: 重构项目结构

- 将server端相关依赖单独防止在server中

interval/server/api/handler/health.go

@@ -0,0 +1,10 @@
+package handler
+
+import "net/http"
+
+func Health(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	if _, err := w.Write([]byte("OK")); err != nil {
+		http.Error(w, "failed to write response", http.StatusInternalServerError)
+	}
+}