fix: 电商页面 KeepAlive 容器使用绝对定位铺满视口，解决底部留白问题

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/App.tsx

@@ -1234,10 +1234,13 @@ function App() {
         <PageTransition viewKey={activeView}>
           {activePage}
         </PageTransition>
+      </Suspense>
+      </ErrorBoundary>
 
-        {/* KeepAlive: EcommercePage stays mounted once visited */}
+      {/* KeepAlive: EcommercePage stays mounted once visited, hidden via display:none */}
       {ecommerceEverMounted && (
-          <div style={{ display: isEcommerceActive ? undefined : "none" }}>
+        <div className="keepalive-ecommerce" style={{ display: isEcommerceActive ? undefined : "none" }}>
+          <Suspense fallback={null}>
             <EcommercePage
               projects={projects}
               isAuthenticated={Boolean(session)}
@@ -1250,10 +1253,9 @@ function App() {
               initialTemplate={pendingEcommerceTemplate}
               onInitialTemplateConsumed={() => setPendingEcommerceTemplate(null)}
             />
+          </Suspense>
         </div>
       )}
-      </Suspense>
-      </ErrorBoundary>
 
       {loginPromptOpen && pendingAction ? (
         <div className="login-gate-modal" role="dialog" aria-modal="true" aria-labelledby="login-gate-title">

src/styles/shell/app-shell.css

@@ -559,12 +559,20 @@
 }
 
 .web-shell__page {
+  position: relative;
   flex: 1;
   min-height: 0;
   overflow: auto;
   scrollbar-color: rgba(var(--accent-rgb), 0.42) transparent;
 }
 
+.keepalive-ecommerce {
+  position: absolute;
+  inset: 0;
+  z-index: 1;
+  overflow: hidden;
+}
+
 /* ── Info button & popover ────────────────────── */
 .info-button {
   display: inline-grid;