feat: Refactor cart storage to use API architecture

Move store_cart functionality from main EventsController to API namespace:
- Add store_cart method to Api::V1::EventsController with API key bypass
- Remove store_cart from main EventsController
- Update routes to use RESTful API endpoint structure
- Maintain session-based cart storage for frontend compatibility

app/controllers/events_controller.rb

@@ -6,7 +6,7 @@ class EventsController < ApplicationController
   include StripeConcern
 
   before_action :authenticate_user!, only: [ :checkout, :process_names, :payment_success, :download_ticket ]
-  before_action :set_event, only: [ :show, :checkout, :process_names, :store_cart ]
+  before_action :set_event, only: [ :show, :checkout, :process_names ]
 
   # Display all events
   def index
@@ -91,16 +91,6 @@ class EventsController < ApplicationController
     process_payment(cart_data)
   end
 
-  # Store cart data in session (AJAX endpoint)
-  def store_cart
-    cart_data = params[:cart] || {}
-    session[:pending_cart] = cart_data
-
-    render json: { status: "success", message: "Cart stored successfully" }
-  rescue => e
-    Rails.logger.error "Error storing cart: #{e.message}"
-    render json: { status: "error", message: "Failed to store cart" }, status: 500
-  end
 
   # Handle successful payment
   def payment_success