chore(app): scaffold tauri 2 + react + vite, window launches

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src-tauri/src/lib.rs

@@ -0,0 +1,6 @@
+#[cfg_attr(mobile, tauri::mobile_entry_point)]
+pub fn run() {
+    tauri::Builder::default()
+        .run(tauri::generate_context!())
+        .expect("error while running spacesh");
+}

app/src-tauri/src/main.rs

@@ -0,0 +1,5 @@
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
+
+fn main() {
+    spacesh_app_lib::run();
+}