Convert dangrubb.net to Astro framework

- Migrated main site, blog, CV, and music sections to Astro
- Component-based architecture with layouts
- JSON-based blog posts
- Static site generation
- Preserved original styling and functionality

src/pages/404.astro

@@ -0,0 +1,28 @@
+---
+import Base from '../layouts/Base.astro';
+---
+
+<Base title="Page Not Found">
+  <div class="not-found">
+    <h1>Page Not Found</h1>
+    <p>This page does not exist yet.</p>
+    <p class="small-text">Stay tuned.</p>
+  </div>
+</Base>
+
+<style>
+  .not-found {
+    display: flex;
+    flex-direction: column;
+    justify-content: center;
+    align-items: center;
+    height: 100vh;
+    text-align: center;
+    background: #123425;
+    color: white;
+    font-family: Arial, sans-serif;
+  }
+  h1 { font-size: 3rem; margin: 0.5em 0; }
+  p { font-size: 1.2rem; margin: 0.5em 0; }
+  .small-text { font-size: 1rem; margin-top: 0.5em; }
+</style>