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/game/add/page.tsx

@@ -0,0 +1,30 @@
+import { redirect } from "next/navigation"
+import { headers } from "next/headers"
+import { auth } from "@/lib/auth"
+import { NonSteamWizard } from "@/components/wizard/non-steam-wizard"
+
+export const dynamic = "force-dynamic"
+
+export const metadata = {
+  title: "Add Non-Steam Game",
+}
+
+export default async function AddGamePage() {
+  const h = await headers()
+  const session = await auth.api.getSession({ headers: h })
+  if (!session?.user) {
+    redirect("/login")
+  }
+
+  return (
+    <div className="max-w-3xl mx-auto px-4 py-8 w-full">
+      <div className="mb-8">
+        <h1 className="text-2xl font-bold mb-2">Add a Game</h1>
+        <p className="text-sm text-text/60">
+          Add a non-Steam game to DeckyVault. Search for cover art, set platform support, and submit.
+        </p>
+      </div>
+      <NonSteamWizard />
+    </div>
+  )
+}