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/lib/storage/index.ts

@@ -0,0 +1,11 @@
+export {
+  uploadObject,
+  deleteObject,
+  listObjects,
+  getObjectMetadata,
+  isR2Configured,
+  getR2PublicUrl,
+  isR2Url,
+  getR2ConfigStatus,
+} from "./r2-client"
+export type { ObjectInfo, ObjectMetadata } from "./r2-client"