* feat: add invoice URL to proration and test seed scripts
- Add invoiceUrl field to MonthlyProration schema
- Update billing service to return hosted_invoice_url after finalizing
- Save invoice URL when creating proration invoices
- Add seed script for testing proration with real Stripe data
- Add cleanup script for test data removal
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
* add invoice url
* add invoice URL to tests
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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
