Feat: Pagination and palette caching for scale

- Add pagination to products and made-to-order pages (20 per page)
- Cache color palette separately for ready-made and personalised
- Fix category queries to use select instead of include
- Calculate total page count for pagination UI
- Add Previous/Next pagination controls

Solves N+1 query problem on color palette generation. With 100+ products:
- Before: Loading all 10,000 products just for color palette
- After: Load palette once (cached 5 mins), show 20 products per page

.claude/settings.local.json

@@ -154,7 +154,8 @@
       "PowerShell(Stop-Process -Id 30912 -Force -ErrorAction SilentlyContinue)",
       "Bash(psql postgresql://postgres:craft2prints@192.168.0.190:5432/craft2prints -c ' *)",
       "Bash(node scripts/add-indexes.js)",
-      "Bash(curl -s http://127.0.0.1:3000)"
+      "Bash(curl -s http://127.0.0.1:3000)",
+      "Bash(curl -s http://127.0.0.1:3000/products)"
     ]
   }
 }