Notificaciones nativas: plugin notification + autostart + bandeja

- tauri-plugin-notification (la web lo invoca vía window.__TAURI__ con withGlobalTauri).
- tauri-plugin-autostart: arranca al iniciar sesión.
- Bandeja del sistema (Abrir/Salir) y cerrar la ventana = ocultar a la bandeja,
  para que la app siga notificando en segundo plano.
- capabilities: notification:default + remote acotado a os.labstreamsas.com.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src-tauri/Cargo.toml

@@ -14,7 +14,9 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 tauri-build = { version = "2", features = [] }
 
 [dependencies]
-tauri = { version = "2", features = [] }
+tauri = { version = "2", features = ["tray-icon"] }
 tauri-plugin-opener = "2"
+tauri-plugin-notification = "2"
+tauri-plugin-autostart = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"