Add paragraph spacing to prose content styling

Add proper margin (my-4) to paragraphs in Tiptap-rendered content.
This ensures proper spacing between paragraphs when displaying
rich text content in product detail pages and other areas.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

supabase/migrations/20241225_add_webinar_duration.sql

@@ -0,0 +1,7 @@
+-- Add duration_minutes column to products table
+-- This column stores the duration in minutes for webinar and consulting products
+ALTER TABLE products
+ADD COLUMN duration_minutes INTEGER;
+
+-- Add comment for documentation
+COMMENT ON COLUMN products.duration_minutes IS 'Duration in minutes for webinars and consulting sessions';