feat: add push notification settings to user profile and update related functionality

backend/models/user.py

@@ -24,6 +24,7 @@ class User(BaseModel):
     token_version: int = 0
     timezone: str | None = None
     email_digest_enabled: bool = True
+    push_notifications_enabled: bool = True
 
     @classmethod
     def from_dict(cls, d: dict):
@@ -49,6 +50,7 @@ class User(BaseModel):
             token_version=d.get('token_version', 0),
             timezone=d.get('timezone'),
             email_digest_enabled=d.get('email_digest_enabled', True),
+            push_notifications_enabled=d.get('push_notifications_enabled', True),
             id=d.get('id'),
             created_at=d.get('created_at'),
             updated_at=d.get('updated_at')
@@ -79,5 +81,6 @@ class User(BaseModel):
             'token_version': self.token_version,
             'timezone': self.timezone,
             'email_digest_enabled': self.email_digest_enabled,
+            'push_notifications_enabled': self.push_notifications_enabled,
         })
         return base