Add meal v2 flow and user timezone support

Introduces a new add_meal_v2 blueprint with barcode scanning, item search, and improved meal logging UI. Adds user timezone support: login form now captures timezone, User model and database schema updated, and timezone is set on login. Refactors templates and forms to support these changes, and removes the old login template.

models.py

@@ -4,6 +4,7 @@ from application import db
 from typing import Optional
 from forms import FoodItemForm
 from datetime import datetime, timezone, date
+from application.utils import is_valid_timezone
 
 
 class User(UserMixin, db.Model):
@@ -11,6 +12,7 @@ class User(UserMixin, db.Model):
     id = db.Column(db.Integer, primary_key=True)
     username = db.Column(db.String(150), unique=True, nullable=False)
     password = db.Column(db.String, nullable=False)
+    timezone = db.Column(db.String(64), nullable=False, default="UTC")
     is_admin = db.Column(db.Boolean, nullable=False, default=False)
     must_change_password = db.Column(db.Boolean, nullable=False, default=False)
 
@@ -39,6 +41,10 @@ class User(UserMixin, db.Model):
     def set_pw_change(self, change: bool) -> None:
         self.must_change_password = change
 
+    def set_timezone(self, tz: str) -> None:
+        if is_valid_timezone(tz):
+            self.timezone = tz
+
 
 class Unit(db.Model):
     __tablename__ = "unit"