feat: deep linking for hosted URLs and openconcho:// scheme

Add /explore redirect route that maps Honcho's deep-link shape
(?workspace=...&view=...&session=...) onto our existing flat routes,
so any app.honcho.dev URL works against a self-hosted instance by
swapping the host.

Wire tauri-plugin-deep-link to register the openconcho:// scheme on
desktop and forward incoming URLs into the router on launch and at
runtime.

packages/desktop/src-tauri/src/lib.rs

@@ -3,6 +3,7 @@ pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_http::init())
         .plugin(tauri_plugin_shell::init())
+        .plugin(tauri_plugin_deep_link::init())
         .run(tauri::generate_context!())
         .expect("error while running tauri application");
 }