Fix refill-only colors to have 0 spools instead of 1

- Add migration to correct 14 colors that should be refill-only
- Create helper script for applying the fix
- Add frontend tracking for refill-only colors
- Update README with current project state
- Add development guidance documentation

src/data/refillOnlyColors.ts

@@ -0,0 +1,25 @@
+// Colors that are only available as refills (no regular spools)
+export const refillOnlyColors = [
+  'Nardo Gray',
+  'Blue Grey',
+  'Blue Gray',  // Alternative spelling
+  'Light Gray',
+  'Brown',
+  'Beige',
+  'Bronze',
+  'Purple',
+  'Cobalt Blue',
+  'Turquoise',
+  'Bright Green',
+  'Yellow',
+  'Gold',
+  'Orange',
+  'Maroon Red'
+];
+
+// Helper function to check if a color is refill-only
+export const isRefillOnly = (colorName: string): boolean => {
+  return refillOnlyColors.some(
+    color => color.toLowerCase() === colorName.toLowerCase()
+  );
+};