PROVIDER org implementation — flip ENABLE_PROVIDER_ORGS

[teetangh]

Full checklist for enabling PROVIDER organizations:

• Verify all 501-gated routes (payouts, payout-account, consultants) work with flag on
• Test ORG_CONSULTANT role in member add/invite flows
• Wire 3-way earnings split in earnings-service.ts
• Test payout batch creation for org payouts
• End-to-end smoke test with a real PROVIDER org

Schema and code paths already exist — this is about verification and the earnings split.

Reference: PR #655, lib/feature-flags.ts, Issue #646.

[teetangh]

Consolidated into a single enterprise tracker issue.