Add admin check and update FoodItems model

Introduced an admin_required check for all admin routes using Flask-Login's current_user. Updated the FoodItems model to use per-100g nutritional fields and removed unit relationships. Seed script now creates both admin and regular user accounts.

application/admin/routes.py

@@ -1,4 +1,6 @@
-from flask import Blueprint, render_template
+from flask import Blueprint, render_template, abort
+from flask_login import current_user
+from models import FoodItems
 
 admin_bp = Blueprint(
     "admin",
@@ -8,6 +10,13 @@ admin_bp = Blueprint(
 )
 
 
+@admin_bp.before_request
+def admin_required():
+    if not current_user.is_admin:
+        abort(403)
+
+
 @admin_bp.route("/food_items", methods=["GET"])
 def food_items():
-    return render_template("food_items.html")
+    items = FoodItems.query.all()
+    return render_template("food_items.html", items=items)