Here's the `user.py` file for the `app/api/v1/models/` directory of the `blog_app` FastAPI backend:

from typing import Optional
from sqlalchemy import Column, ForeignKey, Integer, String, Text
from sqlalchemy.orm import relationship
from app.api.db.database import Base

class User(Base):
    __tablename__ = 'user'

    id = Column(Integer, primary_key=True, index=True)
    username = Column(String, unique=True, index=True, nullable=False)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)
    is_active = Column(Integer, default=1)
    bio = Column(Text, nullable=True)

    posts = relationship("Post", back_populates="author")

    def __repr__(self):
        return f"User(id={self.id}, username='{self.username}', email='{self.email}')"

Explanation:

5. Defined columns for the `User` model:
   - `id`: Integer primary key with index
   - `username`: String, unique, indexed, and non-nullable
   - `email`: String, unique, indexed, and non-nullable
   - `hashed_password`: String, non-nullable
   - `is_active`: Integer with a default value of 1
   - `bio`: Text, nullable

Note: This code assumes that the `Post` model is defined in a separate file and imported accordingly. Additionally, you may need to adjust the imports and paths based on your project structure and dependencies.