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

config/routes.rb

@@ -39,7 +39,6 @@ Rails.application.routes.draw do
   # === Events ===
   get "events",                      to: "events#index",           as: "events"
   get "events/:slug.:id",            to: "events#show",            as: "event"
-  post "events/:slug.:id/store_cart", to: "events#store_cart",     as: "store_cart"
 
   # === Tickets ===
   get "events/:slug.:id/tickets/new",      to: "tickets#new", as: "ticket_new"
@@ -64,7 +63,11 @@ Rails.application.routes.draw do
   namespace :api do
     namespace :v1 do
       # RESTful routes for event management
-      resources :events, only: [ :index, :show, :create, :update, :destroy ]
+      resources :events, only: [ :index, :show, :create, :update, :destroy ] do
+        member do
+          post :store_cart
+        end
+      end
       # resources :bundles, only: [ :index, :show, :create, :update, :destroy ]