Add user dashboard and per-user food item ownership

Introduces a user dashboard route and template, moving dashboard logic to a user blueprint. FoodItem now has an owner_id field and a unique constraint on (barcode, owner_id), with relationships set up in the User model. Updates food item creation to associate with the current user, and adds a utility script for dropping a temporary table.

application/admin/routes.py

@@ -32,6 +32,7 @@ def barcode_test():
 def delete_food(id):
     item = FoodItem.query.get(id)
     if item:
+        # if item.owner_id == current_user.id:
         db.session.delete(item)
         db.session.commit()
     return redirect(url_for("admin.food_items"))