refactor: convert to bun workspaces monorepo

- Move web app into apps/web/
- Create packages/shared/ with shared types
- Create plugins/decky-vault/ scaffold
- Root package.json manages workspaces only

apps/web/app/(manage)/manage/benchmarks/page.tsx

@@ -0,0 +1,10 @@
+import type { Metadata } from "next"
+import { BenchmarksClient } from "./benchmarks-client"
+
+export const metadata: Metadata = {
+  title: "Benchmarks",
+}
+
+export default function BenchmarksPage() {
+  return <BenchmarksClient />
+}