Design: Ticket tear-off stub bespoke layout

[melvincarvalho]

Design PR — edits app.js + app.css only (no app files touched).

• Ticket gets a tear-off event stub layout (class .card.ticket-stub)
  • Horizontal ticket-shaped card with main body (left) and stub side (right)
  • Perforation divider: dashed border + semicircular notch circles (top & bottom)
  • Event name as big bold title, description as subtitle
  • Meta grid: Attendee + Issued date
  • Stub side: ticket number in monospace (rotated 90°), price badge (dark pill), ADMIT ONE label, icon watermark
  • Dark mode support
  • Mobile responsive: stacks vertically, perforation becomes horizontal, stub side becomes row

Gate: 324 apps pass. Task: #IssDesign2_Ticket.