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 */}
-        {ecommerceEverMounted && (
-          <div style={{ display: isEcommerceActive ? undefined : "none" }}>
+      {/* KeepAlive: EcommercePage stays mounted once visited, hidden via display:none */}
+      {ecommerceEverMounted && (
+        <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)}
             />
-          </div>
-        )}
-      </Suspense>
-      </ErrorBoundary>
+          </Suspense>
+        </div>
+      )}
 
       {loginPromptOpen && pendingAction ? (
         <div className="login-gate-modal" role="dialog" aria-modal="true" aria-labelledby="login-gate-title">