Patron QR ordering — session codes and check joining

The patron QR ordering system lets guests order directly from their phones without a server.

Generating a session code:
1. Tap any table in the floor plan to open the order panel
2. Tap "Generate Session Code" — a 6-character code and QR code appear
3. Guests scan the QR or type the code at your ordering URL to access the digital menu
4. The code expires automatically (shown at the top of the code screen)

Patron ordering flow:
• Guests see your full menu, add items, leave special notes, and place their order
• When they place their order, Turtini asks whether they want to join an existing check at the table or keep their own separate check

Joining an existing check:
If other patrons have already ordered at the same table, a list of active checks appears on the patron's screen (showing item count and total for each). They can tap a check to add their order to it, or choose "Keep my check separate" to start a new check.

Staff view:
Orders placed via patron QR appear in the floor plan and kitchen display exactly like server-entered orders. Multiple-check tables show all active checks stacked in the order panel, each labeled with its source (Patron or server).