feat(splashscreen): enhance startup sequence and splashscreen handling

This update improves the splashscreen management during application startup. The splashscreen will now remain visible for a minimum duration and will only close after the main application is ready, ensuring a smoother user experience.

- Introduced a new startup sequence to manage background tasks.
- Added error handling for splashscreen closure to maintain functionality.
- Optimized the timing for displaying and hiding the splashscreen.

src/main.ts

@@ -1,5 +1,4 @@
 import { mount } from "svelte";
-import { invoke } from "@tauri-apps/api/core";
 
 import App from "./App.svelte";
 import "./app.css";
@@ -12,8 +11,4 @@ if (!target) {
 
 const app = mount(App, { target });
 
-void invoke("close_splashscreen").catch(() => {
-  // Browser preview and failed startup paths should keep working without Tauri.
-});
-
 export default app;