Add design and product documentation

PRODUCT.md

@@ -0,0 +1,21 @@
+# Product — Northyard Residences
+
+Status: approved baseline.
+
+## Audience and job
+
+Home buyers and advisers need to understand the development, compare available apartments, inspect plans and amenities, estimate financing, and request a qualified consultation.
+
+## Primary journeys
+
+1. Understand location, architecture, amenities, and delivery status.
+2. Filter apartments and inspect plan, area, floor, orientation, price, and availability.
+3. Explore financing and submit a contextual enquiry.
+
+## Non-goals
+
+- No fabricated availability, guaranteed investment returns, or hidden price conditions.
+
+## Success criteria
+
+Apartment comparison is clear, factual claims are sourced, and the enquiry preserves the selected property context.