Refactor login flow to use auth blueprint

Moved login route and logic from app.py to application/auth/routes.py under the 'auth' blueprint. Updated all references to the login route to use 'auth.login'. Added a dedicated login.html template under application/auth/templates. Adjusted login_required utility and default_return logic for consistency.

application/auth/routes.py

@@ -1,13 +1,30 @@
-from flask import (
-    Blueprint,
-)
-from application.utils import login_required
+from flask import Blueprint, request, render_template
+from flask_login import current_user, login_user
+from forms import LoginForm
+from models import User
+from application.utils import default_return
 
 bp = Blueprint(
-    "user",
+    "auth",
     __name__,
     template_folder="templates",
 )
 
 
-bp.before_request(login_required)
+@bp.route("/login", methods=["GET", "POST"])
+def login():
+    if current_user.is_authenticated:
+        return default_return()
+
+    form = LoginForm()
+    if form.validate_on_submit():
+        user = User.query.filter_by(username=form.username.data).first()
+        if user and user.check_password(password=form.password.data):
+            # User found and password correct
+            next_page = request.args.get("next")  # Get next page if given
+            login_user(user)  # Log in the user
+            return default_return(next_page=next_page)
+        else:
+            pass
+            # invalid user
+    return render_template("login.html", form=form)