feat(web): migrate application shell to TanStack Start

- replace the legacy client-only Vite bootstrap with TanStack Router routes, Start SSR, and Nitro output

- compose the reusable layout, navigation, appearance, chats, and notifications blocks with application-owned data

- persist UI preferences through server functions and initialize theme, sidebar, and breakpoint state before hydration

- add React Query, hotkey, toaster, and responsive dashboard integration

- add application-owned Lingui configuration and catalogs, mount the runtime provider, and lazily enable I18nDevtool in development

- remove superseded HTML, main entry, theme provider, and application ESLint configuration

apps/web/src/i18n/app-i18n-provider.tsx

@@ -0,0 +1,51 @@
+import { lazy, Suspense, type PropsWithChildren } from "react"
+import { I18nProvider, type LocaleDefinition } from "@workspace/i18n"
+
+import { messages as englishMessages } from "@/locales/en/messages"
+import { messages as simplifiedChineseMessages } from "@/locales/zh-Hans/messages"
+
+const I18nDevtool = import.meta.env.DEV
+  ? lazy(() =>
+      import("@workspace/i18n/devtool").then((module) => ({
+        default: module.I18nDevtool,
+      }))
+    )
+  : null
+
+export const appLocales = [
+  {
+    label: "English",
+    locale: "en",
+  },
+  {
+    label: "简体中文",
+    locale: "zh-Hans",
+  },
+] as const satisfies readonly LocaleDefinition[]
+
+export type AppLocale = (typeof appLocales)[number]["locale"]
+
+const appCatalogs = {
+  en: englishMessages,
+  "zh-Hans": simplifiedChineseMessages,
+}
+
+export interface AppI18nProviderProps extends PropsWithChildren {
+  locale?: AppLocale
+}
+
+export function AppI18nProvider({
+  children,
+  locale = "zh-Hans",
+}: AppI18nProviderProps) {
+  return (
+    <I18nProvider catalogs={appCatalogs} locale={locale} locales={appLocales}>
+      {children}
+      {I18nDevtool && (
+        <Suspense fallback={null}>
+          <I18nDevtool dark={"ui\\:dark"} />
+        </Suspense>
+      )}
+    </I18nProvider>
+  )
+}