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- remove superseded HTML, main entry, theme provider, and application ESLint configuration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/router.tsx

@@ -0,0 +1,11 @@
+import { createRouter } from "@tanstack/react-router"
+
+import { routeTree } from "./route-tree.gen"
+
+export function getRouter() {
+  return createRouter({
+    routeTree,
+    defaultPreload: "intent",
+    scrollRestoration: true,
+  })
+}