feat(docs): add custom 404 page

Author: chenxin-yan

apps/docs/astro.config.mjs

@@ -13,7 +13,6 @@ export default defineConfig({
         light: "./src/assets/logo.svg",
         dark: "./src/assets/logo_dark.svg",
         replacesTitle: true,
-        alt: "AlbertPlus logo",
       },
       customCss: ["./src/styles/theme.css"],
       favicon: "/favicon.ico",

apps/docs/src/content/docs/404.md

@@ -0,0 +1,15 @@
+---
+title: "404"
+template: splash
+editUrl: false
+hero:
+  title: "404"
+  tagline: Page not found. Check the URL or try using the search bar.
+---
+
+### Quick Links
+
+- [Overview](/overview)
+- [Getting Started](/getting-started/quick-start)
+- [Architecture](/architecture/overview)
+- [Contributing](/contributing)