feat: Display ticket based on `qr_code` field

- Previously ticket was displayed using id which is too easy to find
- Now the URL takes ``qr_code`` field as parameters

app/models/ticket.rb

@@ -70,7 +70,6 @@ class Ticket < ApplicationRecord
     self.qr_code = "#{id || 'temp'}-#{Time.current.to_i}-#{SecureRandom.hex(4)}"
   end
 
-
   def draft?
     status == "draft"
   end