Add design and product documentation

DESIGN.md

@@ -0,0 +1,12 @@
+# Design — Juniper Table
+
+## Direction
+
+Seasonal editorial hospitality: warm natural color, tactile food imagery, refined type, and booking-led composition without luxury clichés.
+
+## System
+
+- Let menu typography and photography lead; avoid repetitive promotional cards.
+- Booking controls expose availability and validation states clearly.
+- Motion is slow and restrained, never delaying access to menu or booking.
+- Mobile places service window, party size, allergy context, and confirmation expectations in sequence.