docs: update AGENT.md, CLIENT_DELIVERY.md, README.md, IFNEX_Pro_Backlog.md for phase 3.7
Phase 3.7 (Currency refactor + Manual invoices) is now complete.
Update all project documentation to reflect:
- AGENT.md 1.4: add IRR-only architecture section (4.13), wallet-centric
architecture section (4.14), manual invoices (4.14), 4-quadrant rates
(4.15). Add currency red lines to section 7. Restructure section 9
(remaining work) into 3.6 (done), 3.7 (done), 3.8 (future).
- CLIENT_DELIVERY.md: header updated to phase 3.7 complete. Add
section 15.2 with all phase 3.7 deliverables. Update 15.3 remaining
list with future Pro features.
- README.md: add IRR-only, 4-quadrant, manual invoices to key
features. Add phase 3.7 section (100% complete).
- IFNEX_Pro_Backlog.md: add summary table for 5 Pro features, plus
prerequisites section for configurable base currency.
Wallet-centric architecture confirmed: all 4 payment paths (order,
invoice, credit settlement, deposit) flow through the wallet, with
6 transaction types. Race conditions handled with lockForUpdate.
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