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/robots.ts

@@ -0,0 +1,14 @@
+import type { MetadataRoute } from "next"
+
+export default function robots(): MetadataRoute.Robots {
+    return {
+        rules: [
+            {
+                userAgent: "*",
+                allow: "/",
+                disallow: ["/manage", "/api"],
+            },
+        ],
+        sitemap: "https://deckyvault.xyz/sitemap.xml",
+    }
+}