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.

apps/mall/pages/user.vue

@@ -14,12 +14,15 @@ const menuGroups = computed(() => [
       { label: t("user.addresses"), to: "/user/addresses" },
       { label: t("user.coupons"), to: "/user/coupons" },
       { label: t("user.aftersalesTitle"), to: "/user/aftersales" },
+      { label: t("messaging.title"), to: "/user/messages" },
     ],
   },
   {
     title: t("user.memberCenter"),
     items: [
       { label: t("user.dashboard"), to: "/user" },
+      { label: t("membership.entry"), to: "/user/membership" },
+      { label: t("wallet.title"), to: "/user/wallet" },
       { label: t("user.favorites"), to: "/user/favorites" },
       { label: t("user.invoices"), to: "/user/invoices" },
     ],