feat(club-001): club core backend: anonymous members, devices, ledger, cashback config

work/artifacts/CLUB-001/documenter.md

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+# CLUB-001 — Documentation notes
+
+## New backend endpoints
+- `GET /club/config`
+- `POST /club/join`
+- `GET /club/me`
+- `GET /club/movements`
+- `GET /admin/club/settings`
+- `PATCH /admin/club/settings`
+
+## Contract notes
+- Anonymous Club identity is device-based for now.
+- Client receives the raw `deviceToken` once; database stores only `device_token_hash`.
+- The backend also persists the token in cookie `mdv_club` and accepts it again via cookie or `x-club-device-token` header.
+- `club_transactions` is the source of truth; `club_members.current_balance_cents` is a transactional cache.
+- Cashback is configurable through `store_settings` (`club_cashback_bps`) instead of hardcoded constants.
+
+## Scope boundary
+- CLUB-001 ships backend foundations only.
+- PWA screens, digital card UI, TPV integration, recovery flow and account linking remain for later CLUB phases.