Fix #67: Update hero CTA and speaking page reel placeholder

- Change homepage hero CTA from 'Watch the Reel' to 'Explore Speaking'
- Update speaking page reel placeholder to acknowledge missing video
- Add direction to signature talks below the reel placeholder

#50 and #47 already resolved in codebase:
- Hero images exist in public/images/
- Favicon exists (favicon.ico and favicon.svg)
- Manifest.json exists

src/pages/index.astro

@@ -30,7 +30,7 @@ import PillarCard from '../components/PillarCard.astro';
       </p>
       <div class="hero-actions">
         <a href="/speaking#book" class="btn btn-primary">Book Scott for Your Event</a>
-        <a href="/speaking" class="btn btn-outline">Watch the Reel</a>
+        <a href="/speaking" class="btn btn-outline">Explore Speaking</a>
       </div>
     </div>
   </section>