Remove all hotlinked Unsplash images — download locally, replace 14 404s

- Downloaded all 31 Unsplash images to photos/ directory
- Found 14 URLs returning 404; replaced with working equivalents:
  about: book-room, hard-drives, forest-child
  human-body: digestive-system, human-eye
  inventions: gears (x2), lab-glassware
  maps/phenomena: old-map (x2), ornate-globe, earth-orbit
  natural-world: migrating-birds
  phenomena: lightning-storm, ferrofluid
  space: voyager-record
- Updated all 8 HTML files to reference local photos/ instead of Unsplash CDN
- Fixed broken ammonite clipart reference (fossil -> existing image)
- Updated CSS clipart hover effects and responsive rules

about.html

@@ -28,7 +28,7 @@
       </ul>
     </nav>
 
-    <img src="img/old-leather-book-illustration.png" alt="" class="clipart-section">
+    <img src="img/steampunk-book-and-goggles-image.png" alt="" class="clipart-section">
 
     <div class="section-bar">About This Site</div>
 
@@ -44,7 +44,7 @@
     </div>
 
     <div class="figure-right">
-      <img src="https://images.unsplash.com/photo-1507842218343-f13504bf4157?w=600&h=400&fit=crop" alt="A warm, book-filled room — the spiritual home of Dangerous Wonder">
+      <img src="photos/photo-1521587760476-6c12a4b040da_600x400.jpg" alt="A warm, book-filled room — the spiritual home of Dangerous Wonder">
       <p class="figure-caption">The kind of place where curiosity lives. Dangerous Wonder was born at a kitchen table that looked very much like this.</p>
     </div>
 
@@ -73,7 +73,7 @@
       <p>A hard drive failure in August of 2011 nearly killed Dangerous Wonder. Marguerite had not backed up the site in eleven months. For three agonizing days, the site existed only on a failing RAID array and in the Wayback Machine. A data recovery service in Seattle managed to salvage 98% of the files. The remaining 2% — mostly forum posts from 2008 and one deeply loved page about the invention of the pencil — were never recovered. Marguerite now backs up every Sunday at 3:00 AM using a cron job and three separate cloud services. She has not missed one since.</p>
 
       <div class="figure">
-        <img src="https://images.unsplash.com/photo-1558618666-fcd25c85f82e?w=600&h=400&fit=crop" alt="Old hard drives and cables — the infrastructure of an earlier web">
+        <img src="photos/photo-1550751827-4bd374c3f58b_600x400.jpg" alt="Old hard drives and cables — the infrastructure of an earlier web">
         <p class="figure-caption">The tools of the trade. For years, Dangerous Wonder lived on hardware not unlike this.</p>
       </div>
 
@@ -119,7 +119,7 @@
       <img src="img/vintage-reading-glasses-on-book-image.png" alt="" class="clipart-right">
 
       <div class="figure-left">
-        <img src="https://images.unsplash.com/photo-1473186509769-9c81ecead3f1?w=600&h=400&fit=crop" alt="A child gazing up at a towering forest">
+        <img src="photos/photo-1448375240586-882707db888b_600x400.jpg" alt="A child gazing up at a towering forest">
         <p class="figure-caption">Wonder is not passive. It demands that you look closer, step further, ask one more question.</p>
       </div>
 
@@ -215,4 +215,4 @@
 
   <script src="js/main.js"></script>
 </body>
-</html>
+</html>