fix: set unprocessable entity status on login failure

- Change the render method to include a status of
  :unprocessable_entity when the email/password combination
  is invalid.
- This change improves the API response for invalid login
  attempts, allowing clients to better handle errors.

app/controllers/sessions_controller.rb

@@ -14,7 +14,7 @@ class SessionsController < ApplicationController
       redirect_to forwarding_url || user
     else
       flash.now[:danger] = "Invalid email/password combination"
-      render "new"
+      render "new", status: :unprocessable_entity
     end
   end