fix: Resolve QR code generation errors in ticket PDF creation

- Add validation in TicketPdfGenerator to ensure QR code data integrity
- Use compact() to remove nil values from QR code data hash
- Add error handling in Ticket#generate_qr_code with fallback generation
- Validate QR code data before passing to RQRCode library
- Add proper error logging for QR code generation failures
- Prevent "data must be a String, QRSegment, or an Array" errors

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

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

app/models/ticket.rb

@@ -63,6 +63,10 @@ class Ticket < ApplicationRecord
       self.qr_code = SecureRandom.uuid
       break unless Ticket.exists?(qr_code: qr_code)
     end
+  rescue => e
+    Rails.logger.error "Failed to generate QR code for ticket: #{e.message}"
+    # Generate a simple fallback QR code
+    self.qr_code = "#{id || 'temp'}-#{Time.current.to_i}-#{SecureRandom.hex(4)}"
   end