web: cut over to Vite SPA, retire the Next.js shell (#1444)

Delete the src/app tree, next.config.ts, next-env.d.ts, and the Next-only
guard/header components. Port AppShell/Sidebar/Topbar to react-router and
mount them as a DashboardLayout route over all authenticated routes. Strip
'use client' directives, move globals.css up from the deleted app/ tree,
rewrite tsconfig for Vite/Bundler resolution, drop the next dependency.

Test fixes the port surfaced: jsdom v29 has no window.matchMedia (sidebar
breakpoint) so setup.ts stubs it; the router-boundary specs render inside
ThemeProvider because the chrome's ThemeToggle requires the context.

apps/web/tsconfig.json

@@ -1,16 +1,16 @@
 {
   "extends": "../../tsconfig.base.json",
   "compilerOptions": {
-    "target": "ES2017",
+    "target": "ES2022",
     "lib": ["dom", "dom.iterable", "ES2022"],
     "module": "ESNext",
     "moduleResolution": "Bundler",
-    "jsx": "preserve",
-    "plugins": [{ "name": "next" }],
+    "jsx": "react-jsx",
+    "types": ["vite/client"],
     "paths": {
       "@/*": ["./src/*"]
     }
   },
-  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts"],
+  "include": ["src", "vite.config.ts", "vitest.config.ts"],
   "exclude": ["node_modules", "e2e", "playwright.config.ts"]
 }