How can I improve on this flask, sqlalchemy, jwt file in python?

I have created this Flask, SQLAlchemy python file and i want to know how can I improve on it? make it look nicer and some tips and guides if possible.

from flask import Flask, render_template, request, redirect, flash, session, jsonify
from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import DataRequired, EqualTo
from werkzeug.security import check_password_hash, generate_password_hash
from flask_jwt_extended import JWTManager, create_access_token, jwt_required, get_jwt_identity
import sqlite3
import os

app = Flask(__name__)
app.config['SECRET_KEY'] = os.urandom(16).hex()
app.config['JWT_SECRET_KEY'] = os.urandom(16).hex()
jwt = JWTManager(app)

# Connect to the SQLite database
def get_db_connection():
    conn = sqlite3.connect("db.sqlite3", check_same_thread=False)
    return conn

# Create users table if it doesn't exist
def create_users_table():
    conn = get_db_connection()
    c = conn.cursor()
    c.execute('''
    CREATE TABLE IF NOT EXISTS users (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        email TEXT UNIQUE NOT NULL,
        password TEXT NOT NULL
    )
    ''')
    conn.commit()
    conn.close()

class RegistrationForm(FlaskForm):
    email = StringField('Email', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])
    confirmation = PasswordField('Confirm Password', validators=[
        DataRequired(),
        EqualTo('password', message='Passwords must match')
    ])
    submit = SubmitField('Register')

class LoginForm(FlaskForm):
    email = StringField('Email', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])
    submit = SubmitField('Login')

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/register', methods=['GET', 'POST'])
def register():
    form = RegistrationForm()
    if form.validate_on_submit():
        email = form.email.data
        password = form.password.data

        conn = get_db_connection()
        c = conn.cursor()
        c.execute("SELECT * FROM users WHERE email=:email", {"email": email})
        if c.fetchone():
            flash('User already registered')
        else:
            passhash = generate_password_hash(password, method="pbkdf2:sha256", salt_length=16)
            c.execute('INSERT INTO users (email, password) VALUES (:email, :passhash)', {"email": email, "passhash": passhash})
            conn.commit()
            flash('Registered successfully')
            return redirect('/home')
        conn.close()

    return render_template('register.html', form=form)

@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        email = form.email.data
        password = form.password.data

        conn = get_db_connection()
        c = conn.cursor()
        c.execute("SELECT * FROM users WHERE email=:email", {"email": email})
        user = c.fetchone()

        if user is None:
            flash('User not found')
        else:
            passhash = user[2]
            if not check_password_hash(passhash, password):
                flash('Wrong password')
            else:
                access_token = create_access_token(identity=user[0])
                return jsonify(access_token=access_token)
        conn.close()

    return render_template('login.html', form=form)

@app.route('/protected', methods=['GET'])
@jwt_required(refresh=True)
def protected():
    current_user = get_jwt_identity()
    return render_template('protected.html', user=current_user)

@app.route('/logout')
def logout():
    return redirect('/login')

@app.route('/home')
def home():
    return render_template('home.html')

if __name__ == '__main__':
    create_users_table()
    app.run(debug=True)

its just a normal backend file, I'm fairly new to flask and python so I want to see if there is something fundamentally is wrong with this file or there is any improvement i can do

1. You are connecting to db every time you get a request instead of that you can use this g thing which is documented in Flask, or better use flask_sqlalchemy.

2. You are using wtforms with Validators you can use multiple Validators in a field like Email Validator to ensure your data is correct. Like below example:

   email = StringField('Email', validators=[DataRequired(), Email()])
   

3. Do not store bare passwords on db. Also do not encrypt decrypt passwords. Instead use hashing algorithms for password store. You can look what salting is from here. You can use hashlib or werkzeug's generate_password_hash for start points.

4. You can use general error handlers as flask suggests from here.

5. Try to avoid nested if-else blocks if not necessary to use.