feat: add GitHub, YouTube, and website links to about page and footer

Add Source Code section with GitHub repo link and Demo Video section with
YouTube link to the about page. Add footer links to GitHub, YouTube,
mathewguest.com, and zavage-software.com with Bootstrap Icons and themed
hover styling.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/about.html

@@ -38,8 +38,20 @@
 <div class="content-section">
     <h3>📂 Source Code</h3>
     <p>
-        The source code for this project will be available on GitHub.
-        <em>Link coming soon.</em>
+        The source code for this project is available on GitHub:<br>
+        <a href="https://github.com/mathewguest/wordsearch" target="_blank" rel="noopener">
+            <i class="bi bi-github"></i> github.com/mathewguest/wordsearch
+        </a>
+    </p>
+</div>
+
+<div class="content-section">
+    <h3>🎬 Demo Video</h3>
+    <p>
+        Watch a video showing off Claude Code building this project:<br>
+        <a href="https://youtu.be/3Cr4GnvK7co" target="_blank" rel="noopener">
+            <i class="bi bi-youtube"></i> Watch on YouTube
+        </a>
     </p>
 </div>
 {% end %}