create basic backend with login

main-server/app/controllers/application_controller.rb

@@ -0,0 +1,25 @@
+class ApplicationController < ActionController::API
+  include ActionController::HttpAuthentication::Token::ControllerMethods
+
+  before_action :authenticate_request!
+
+  attr_reader :current_user
+
+  private
+
+  def authenticate_request!
+    token = extract_token
+    return render json: { error: "Unauthorized" }, status: :unauthorized unless token
+
+    decoded = JwtService.decode(token)
+    @current_user = User.find_by(id: decoded[:user_id]) if decoded
+    render json: { error: "Unauthorized" }, status: :unauthorized unless @current_user
+  end
+
+  def extract_token
+    auth_header = request.headers["Authorization"]
+    return auth_header.split(" ").last if auth_header&.start_with?("Bearer ")
+
+    params[:token]
+  end
+end