feat(sp9): multi-payer, multi-NPI, SFTP stub for dzinesco/TOC
- providers table seeded with 3 NPIs (Montrose, Delta, Salida)
- payers + payer_configs (per-tx config) join table
- clearhouse singleton (dzinesco identity, SFTP block, filename block)
- config/payers.yaml loader with Pydantic schema validation
- cyclone/edi/filenames.py: HCPF X12 File Naming Standards helpers
- cyclone/clearhouse/sftp.py: stub that copies to ./var/sftp/staging/...
- cyclone/secrets.py: macOS Keychain wrapper via keyring
- 11 new validation rules R200-R210 (CO MAP + HCPF naming)
- 6 new API endpoints (/api/clearhouse/*, /api/config/*, /api/admin/reload-config)
- migration 0007
- 72 new tests (646 total passing, was 574)
See spec: docs/superpowers/specs/2026-06-20-cyclone-multi-payer-npi-sftp-design.md
Tyler
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