feat: 内测申请弹窗 + 电商功能介绍页样式优化

- 新增 BetaApplicationModal 组件，支持文本输入、单/多选、签字等交互

- 顶部通知铃铛左侧添加「内测申请」按钮（脉冲动画）

- 电商功能介绍页等比例放大，减少空白，布局更紧凑

- 右侧卡片区域放大，卡片内容清晰可见

src/components/AppShell.tsx

@@ -19,6 +19,7 @@ import { ossAssets } from "../data/ossAssets";
 import { canManageCommunityCases, canReviewCommunity } from "../features/community-review/communityPermissions";
 import type { WebNavItem, WebNotification, WebUsageSummary, WebUserSession, WebViewKey } from "../types";
 import NotificationCenter from "./NotificationCenter";
+import BetaApplicationModal from "./BetaApplicationModal";
 import { RechargeModal } from "./RechargeModal/RechargeModal";
 import { AnimatedPanel } from "./AnimatedPanel";
 import AdminMonitor from "./AdminMonitor";
@@ -68,6 +69,7 @@ function AppShell({
   const [profileOpen, setProfileOpen] = useState(false);
   const [rechargeOpen, setRechargeOpen] = useState(false);
   const [infoOpen, setInfoOpen] = useState(false);
+  const [betaOpen, setBetaOpen] = useState(false);
   const infoRef = useRef<HTMLDivElement>(null);
   const [openSubmenuKey, setOpenSubmenuKey] = useState<WebViewKey | null>(null);
   const [publicConfig, setPublicConfig] = useState<WebPublicConfig>({});
@@ -335,6 +337,15 @@ function AppShell({
               <span className="brand-lockup__name">OmniAI</span>
             </button>
             <div className="web-topbar__actions">
+              <button
+                type="button"
+                className="beta-apply-button"
+                title="内测申请"
+                aria-label="内测申请"
+                onClick={() => setBetaOpen(true)}
+              >
+                内测申请
+              </button>
               {session && (
                 <NotificationCenter
                   items={notifications}
@@ -491,6 +502,7 @@ function AppShell({
       </div>
       {session?.user.role === "admin" ? <AdminMonitor /> : null}
       <RechargeModal open={rechargeOpen} onClose={() => setRechargeOpen(false)} currentBalance={displayedBalanceCents} />
+      <BetaApplicationModal open={betaOpen} onClose={() => setBetaOpen(false)} />
       <CookieConsentBanner />
     </div>
   );