docs: fix ROADMAP references and move sample content to completed

- Remove reference to deleted sample-content.md
- Move Sample Content to Completed section (it's implemented)
- Note Printify integration in completed features

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ROADMAP.md

@@ -41,16 +41,6 @@ Currently we have `/products` but the original plan included `/collections/:slug
 
 ## Medium Features
 
-### Sample Content Refresh ("Wildprint Studio")
-**Status:** Planned (see `docs/plans/sample-content.md`)
-**Effort:** Medium
-
-Replace current preview data with POD-focused content:
-- 16 products across 5 categories (Art Prints, Apparel, Homewares, Stationery, Accessories)
-- Nature/botanical primary theme with variety
-- UK-focused (prices in £)
-- Printify API integration for automated mockup generation
-
 ### Page Builder (Database-Driven Pages)
 **Status:** Planned (see `docs/plans/page-builder.md`)
 **Effort:** Large
@@ -123,6 +113,12 @@ Phase 9 testing is basic. Areas needing better coverage:
 
 ## Completed (For Reference)
 
+### Sample Content ("Wildprint Studio") ✅
+- 16 POD products across 5 categories
+- Nature/botanical theme with testimonials
+- UK-focused (prices in £)
+- Printify API integration for mockup generation (`mix generate_mockups`)
+
 ### Phase 1-8: Theme Editor ✅
 - Theme settings schema and persistence
 - CSS three-layer architecture