feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/libs/markstream-vue/packages/markdown-parser/components.d.ts

@@ -0,0 +1,14 @@
+/* eslint-disable */
+// @ts-nocheck
+// Generated by unplugin-vue-components
+// Read more: https://github.com/vuejs/core/pull/3399
+// biome-ignore lint: disable
+export {}
+
+/* prettier-ignore */
+declare module 'vue' {
+  export interface GlobalComponents {
+    RouterLink: typeof import('vue-router')['RouterLink']
+    RouterView: typeof import('vue-router')['RouterView']
+  }
+}