Refactor codebase

app/routes/dashboard.py

@@ -1,7 +1,7 @@
 from flask import Blueprint, render_template
 from app.auth import login_required, get_current_user
 from app.db import query, query_one
-from app.utils import calculate_streak
+from app.utils import calculate_streak, calculate_weight_change
 
 bp = Blueprint("dashboard", __name__)
 
@@ -32,11 +32,11 @@ def index():
     weight_change = None
     weight_change_pct = None
     if latest and first_checkin:
-        start_w = float(first_checkin["weight_kg"])
-        current_w = float(latest["weight_kg"])
-        weight_change = round(current_w - start_w, 1)
-        if start_w > 0:
-            weight_change_pct = round((weight_change / start_w) * 100, 1)
+        kg_lost, pct_lost = calculate_weight_change(
+            first_checkin["weight_kg"], latest["weight_kg"]
+        )
+        weight_change = round(-kg_lost, 1)       # negative = gained, positive = lost
+        weight_change_pct = round(-pct_lost, 1)
 
     # Recent check-ins (last 5)
     recent_checkins = query(
@@ -75,4 +75,3 @@ def index():
         milestones=milestones,
         streak=streak,
     )
-