Refactor login_required and add auth blueprint

Moved the login_required logic to a new utils.py for reuse. Added a new auth blueprint and registered it in app.py. Updated user blueprint to use the shared login_required function.

application/auth/routes.py

@@ -0,0 +1,13 @@
+from flask import (
+    Blueprint,
+)
+from application.utils import login_required
+
+bp = Blueprint(
+    "user",
+    __name__,
+    template_folder="templates",
+)
+
+
+bp.before_request(login_required)