Add change password functionality for users

Introduces a change password route, form, and template, allowing authenticated users to update their password. Updates the User model with a method to set the must_change_password flag. Adjusts login and navigation logic to support the new flow and ensures users are redirected to change their password if required.

models.py

@@ -36,6 +36,9 @@ class User(UserMixin, db.Model):
     def change_password(self, password: str) -> None:
         self.password = generate_password_hash(password=password)
 
+    def set_pw_change(self, change: bool) -> None:
+        self.must_change_password = change
+
 
 class Unit(db.Model):
     __tablename__ = "unit"