fix(client): use http extension for fetching on backend

Originally, using the built-in `fetch()` resulted in CORS errors because it was fetching from the "frontend", which doesn't work after building. This commit migrates to Tauri's HTTP plugin, which is made for exactly this scenario.

src-tauri/src/lib.rs

@@ -137,6 +137,7 @@ fn setup_global_shortcut(app: &mut tauri::App) -> Result<(), Box<dyn std::error:
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
+        .plugin(tauri_plugin_http::init())
         .manage(WsState::default())
         .plugin(tauri_plugin_single_instance::init(|app, args, _cwd| {
             if args.len() > 1 && args[1].starts_with("raycast://") {