feat: wave 2 migration (P3, P5, P7 openspec changes)

Implements, verifies, and archives the three remaining Wave 2 changes from
openspec/MIGRATION-PLAN.md.

- add-wallet-settlement (P3): demo recharge, guarded withdrawal freeze and
  one-time admin review, paginated own fund entries, idempotent per-shop
  weekly/monthly settlement statements with commission rate and one-time
  payout confirmation.
- add-merchant-onboarding (P5): personal/enterprise applications with one live
  application per user, guarded review with mandatory rejection reason, and
  transactional shop + owner provisioning returning one-time credentials;
  mall onboarding/status pages and an admin review console.
- add-membership-messaging (P7): platform member levels, append-only growth
  accrual on order completion with guarded one-way leveling, order/shipment/
  refund system messages with unread/read state and soft deletion, plus the
  mall header unread badge.

Backend: migrations 0019-0023, new wallet, settlement, merchant_onboarding,
membership and messaging modules, event hooks in order/fulfillment/aftersale,
and integration suites for each. Shared contract extended and all three
frontends updated; code indexes, domain docs, backend guidelines and the
migration tracker synced.

Verification: cargo test -p vmall-api green twice consecutively; mall, admin
and shop-admin builds pass; browser smoke on every new surface; openspec
validate --all --strict green (33 passed).

The three changes share the @vmall/shared contract, the mall mock adapter and
per-app locale/nav files, so they are committed together to keep every commit
buildable.

docs/TBD-marketing.md

@@ -85,6 +85,11 @@ Recorded so the gap is explicit, not because all of them belong in scope:
   templates (by piece/weight, first+additional fees, free thresholds, region overrides),
   server-side checkout fee computation with per-item snapshots, and a shipping-company
   dictionary validated at ship time.
+- [x] **Merchant onboarding / 商家入驻** — implemented live as `add-merchant-onboarding`:
+  the mall `/merchant/join` + `/merchant/status` pages call the real backend through the
+  `merchantOnboarding` live domain, and the admin review console calls the admin API. No
+  fixture-driven onboarding surface remains in `apps/mall/mock`, so nothing is listed here
+  as a holdout. Wallet/withdrawal and settlement holdouts are likewise live (`add-wallet-settlement`).
 
 ## Deferred designs from general B2B2C storefronts