[optimize](app) Add timestamp to optimize output messages

app.py

@@ -3,6 +3,7 @@ import pandas as pd
 import numpy as np
 from numpy.typing import NDArray
 from pyscipopt import Model, quicksum
+from datetime import datetime
 
 # Define the quality tiers and names for the plants
 PLANTS_TIERS = {
@@ -164,11 +165,14 @@ def calculator(currency, budget, strategy, extra_rate, *amount):
     model.addCons(obj1 <= budget)
 
     # first optimize
-    # model.hideOutput()
+    model.hideOutput()
     model.optimize()
 
     if model.getStatus() == "optimal":
         optimal_total_value = model.getObjVal()
+        print(
+            f"[{datetime.now().strftime('%Y-%m-%d %H:%M:%S')}] First-stage optimal total value: {optimal_total_value}"
+        )
         model.freeTransform()
 
         model.setObjective(