Add food item management and improve barcode workflow

Implemented routes and forms for adding and viewing food items by barcode, including templates for displaying and entering nutritional information. Enhanced the scan workflow to redirect to food item details or entry form. Added admin ability to delete food items. Improved UI for login and scan pages. Updated FoodItem model and form fields for consistency and accuracy.

models.py

@@ -36,26 +36,26 @@ class Unit(db.Model):
 class FoodItem(db.Model):
     __tablename__ = "food_item"
     id = db.Column(db.Integer, primary_key=True)
-    barcode = db.Column(db.Integer)
+    barcode = db.Column(db.Integer, nullable=False)
     name = db.Column(db.String(150), unique=True, nullable=False)
 
     energy_100g = db.Column(db.Integer, nullable=False)
     protein_100g = db.Column(db.Float, nullable=False)
-    carbs_100g = db.Column(db.Integer, nullable=False)
-    sugar_100g = db.Column(db.Integer)
-    fats_100g = db.Column(db.Integer, nullable=False)
-    saturated_fats_100g = db.Column(db.Integer)
+    carbs_100g = db.Column(db.Float, nullable=False)
+    sugar_100g = db.Column(db.Float)
+    fats_100g = db.Column(db.Float, nullable=False)
+    saturated_fats_100g = db.Column(db.Float)
 
     def __init__(
         self,
         name: str,
         energy: int,
         protein: float,
-        carbs: int,
-        fats: int,
-        sugar: Optional[int] = None,
-        saturated_fats: Optional[int] = None,
-        barcode: Optional[int] = None,
+        carbs: float,
+        fats: float,
+        barcode: int,
+        sugar: Optional[float] = None,
+        saturated_fats: Optional[float] = None,
     ):
         self.name = name
         self.energy_100g = energy