docs: Chinese Alipay payout methods require date of birth

[cursor]

Summary

Documents frontend/API change opencollective-frontend#12351 / opencollective-api#12026: payees creating a Chinese Alipay bank transfer payout method through Wise must now provide their date of birth (YYYY-MM-DD) for identity verification.

Docs added/updated

• expenses-and-getting-paid/submitting-expenses/README.md — new "Bank transfer payout methods (Wise)" section covering Alipay date-of-birth requirement
• fiscal-hosts/expense-payment/handling-payment-errors-through-wise.md — guidance for hosts when Alipay payments fail due to missing payee details

Codepaths covered

• Wise bank transfer payout method creation form (PayoutBankInformationForm)
• API injection of dateOfBirth field for chinese_alipay recipient type
• Fiscal host troubleshooting flow for failed Alipay transfers

Knowledge gaps addressed

• Why date of birth is required when setting up Chinese Alipay payout methods
• Format requirement (YYYY-MM-DD) and when to update existing payout methods
• How fiscal hosts should handle payment failures caused by missing payee identity details

Other recent changes reviewed (no doc updates needed)

• #12348 — expense drawer fix for hidden accounts (bug fix; no workflow change)
• #12350 — radix radio group fix (internal)
• #12345 — fiscal host profile hides internal platform billing (covered by open PR docs: fiscal host profile hides internal platform billing transactions #25)
• #12343 — hide Create Contribution Tier card in admin view (admin UI only)
• API repo — dependency updates and internal fixes only