feat(splashscreen): implement a splash screen for application startup

This commit introduces a splash screen that enhances the user experience during application startup. It includes a new HTML file for the splash screen layout and a corresponding icon. The main application logic has been updated to close the splash screen once the main application is ready.

- Added a splash screen HTML and icon for improved visual feedback
- Updated main application logic to manage splash screen visibility
- Enhanced title bar branding with an image instead of SVG

src/main.ts

@@ -1,4 +1,5 @@
 import { mount } from "svelte";
+import { invoke } from "@tauri-apps/api/core";
 
 import App from "./App.svelte";
 import "./app.css";
@@ -9,4 +10,10 @@ if (!target) {
   throw new Error("App target element was not found.");
 }
 
-export default mount(App, { 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;