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/components/shell/SiteFooter.vue

@@ -27,6 +27,11 @@ onBeforeUnmount(() => window.removeEventListener("scroll", onScroll));
         <li>{{ t("shell.footer.v2") }}</li>
         <li>{{ t("shell.footer.v3") }}</li>
         <li>{{ t("shell.footer.v4") }}</li>
+        <li>
+          <NuxtLink to="/merchant/join" class="hover:text-primary">{{
+            t("shell.footer.sellerJoin")
+          }}</NuxtLink>
+        </li>
       </ul>
       <div class="text-muted pt-[30px] pb-5 text-[12px] leading-7">
         <p class="m-0">{{ t("shell.footer.copyright") }}</p>

apps/mall/components/shell/SiteHeader.vue

@@ -2,6 +2,8 @@
 const { t, locale, locales, setLocale } = useI18n();
 const { currency } = usePrefs();
 const cart = useCartStore();
+const session = useSessionStore();
+const { unread, refresh: refreshUnread, setCount } = useUnreadMessages();
 const route = useRoute();
 const router = useRouter();
 
@@ -28,8 +30,26 @@ onMounted(async () => {
     /* keep default */
   }
   void cart.refresh();
+  if (session.isLoggedIn) void refreshUnread();
 });
 
+// The session is restored from localStorage after hydration.
+watch(
+  () => session.isLoggedIn,
+  (loggedIn) => {
+    if (loggedIn) void refreshUnread();
+    else setCount(0);
+  },
+);
+
+// The shell outlives route changes, so page entry is what re-reads the count.
+watch(
+  () => route.fullPath,
+  () => {
+    if (session.isLoggedIn) void refreshUnread();
+  },
+);
+
 const menuOpen = ref(false);
 const isHome = computed(() => route.path === "/");
 // The home page pins the category menu in the hero row instead, so the header
@@ -86,6 +106,23 @@ const showMenu = computed(() => menuOpen.value && !isHome.value);
               >{{ cart.count }}</span
             >
           </NuxtLink>
+          <!-- Anonymous shoppers have no message center, so this entry is
+               client-only until the localStorage session is restored. -->
+          <ClientOnly>
+            <NuxtLink
+              v-if="session.isLoggedIn"
+              to="/user/messages"
+              class="text-muted hover:text-primary relative no-underline transition-colors"
+              :aria-label="t('messaging.unreadBadge', { count: unread })"
+            >
+              {{ t("messaging.title") }}
+              <span
+                v-if="unread > 0"
+                class="bg-danger absolute -top-3 -right-3 rounded-sm px-1 text-[11px] leading-4 text-white"
+                >{{ unread }}</span
+              >
+            </NuxtLink>
+          </ClientOnly>
         </div>
       </div>
 

apps/mall/components/shell/TopBar.vue

@@ -76,7 +76,7 @@ const { t } = useI18n();
         </ClientOnly>
         <li class="text-border px-1">|</li>
         <li>
-          <NuxtLink to="/stores" class="text-primary hover:text-primary-hover px-1">{{
+          <NuxtLink to="/merchant/join" class="text-primary hover:text-primary-hover px-1">{{
             t("shell.sellerJoin")
           }}</NuxtLink>
         </li>