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

css/style.css

@@ -2,7 +2,7 @@
    DANGEROUS WONDER
    A Field Guide to Everything Worth Knowing
    Est. 1999
-   
+
    Style: Utopian Scholastic / DK Book Aesthetic
    Era feel: Late 90s-early 2000s web
    ============================================ */
@@ -548,36 +548,36 @@ p {
   .site-title {
     font-size: 1.8rem;
   }
-  
+
   .card-grid {
     grid-template-columns: 1fr;
   }
-  
+
   .figure-right, .figure-left {
     float: none;
     margin: 16px 0;
     max-width: 100%;
   }
-  
+
   .site-nav a {
     padding: 6px 8px;
     font-size: 0.82rem;
   }
-  
+
   .toc {
     columns: 1;
   }
-  
+
   .clipart-left, .clipart-right {
     float: none;
     margin: 8px auto;
     max-width: 80px;
   }
-  
+
   .clipart-section {
     max-width: 100px;
   }
-  
+
   .clipart-wide {
     max-width: 120px;
   }
@@ -633,8 +633,8 @@ p {
 
 .clipart-divider {
   display: block;
-  margin: 10px auto;
-  max-width: 100px;
+  margin: 40px auto;
+  max-width: 800px;
   opacity: 0.6;
   image-rendering: auto;
   transition: opacity 0.3s, transform 0.3s;
@@ -650,6 +650,16 @@ p {
   transition: opacity 0.3s, transform 0.3s;
 }
 
+.clipart-ultrawide {
+  display: block;
+  margin: 10px auto;
+  max-width: 180px;
+  opacity: 0.8;
+  image-rendering: auto;
+  filter: drop-shadow(1px 2px 3px rgba(0,0,0,0.15));
+  transition: opacity 0.3s, transform 0.3s;
+}
+
 .clipart-left:hover,
 .clipart-right:hover,
 .clipart:hover,
@@ -665,4 +675,4 @@ p {
 .text-small { font-size: 0.85rem; }
 .margin-top { margin-top: 24px; }
 .margin-bottom { margin-bottom: 24px; }
-.clear { clear: both; }
+.clear { clear: both; }