feat: Add booking control during events

- Add allow_booking_during_event boolean field to events (defaults to false)
- Implement booking_allowed? method to check if tickets can be purchased
- Add event_started? and event_ended? helper methods
- Include new option in event edit form with clear explanation
- Display booking policy status on event show page
- Add visual indicator when booking is disabled during ongoing events
- Update controller to permit new parameter

This allows promoters to control whether attendees can purchase tickets
after an event has started, providing flexibility for different event types.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2025_08_23_171354) do
+ActiveRecord::Schema[8.0].define(version: 2025_09_11_063815) do
   create_table "events", charset: "utf8mb4", collation: "utf8mb4_uca1400_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "slug", null: false
@@ -27,6 +27,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_08_23_171354) do
     t.bigint "user_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.boolean "allow_booking_during_event", default: false, null: false
     t.index ["featured"], name: "index_events_on_featured"
     t.index ["latitude", "longitude"], name: "index_events_on_latitude_and_longitude"
     t.index ["state"], name: "index_events_on_state"