feat(shop): add dynamic linked fees to modules

shop/supabase/migrations/20260722100000_add_linked_fee_to_modules.sql

@@ -0,0 +1,3 @@
+-- Add linked_fee_product_id to product_modules table
+ALTER TABLE public.product_modules 
+ADD COLUMN IF NOT EXISTS linked_fee_product_id UUID REFERENCES public.products(id) ON DELETE SET NULL;