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

index.html

@@ -29,7 +29,7 @@
     </nav>
 
     <div style="margin: 28px 0 24px; text-align: center;">
-      <img src="https://images.unsplash.com/photo-1506905925346-21bda4d32df4?w=900&h=300&fit=crop" alt="A vast mountain landscape stretching toward the horizon" style="width:100%; max-width:900px; border: 3px solid #fff; box-shadow: 3px 4px 8px rgba(0,0,0,0.28);">
+      <img src="photos/1506905925346-21bda4d32df4_900x300.jpg" alt="A vast mountain landscape stretching toward the horizon" style="width:100%; max-width:900px; border: 3px solid #fff; box-shadow: 3px 4px 8px rgba(0,0,0,0.28);">
       <p class="figure-caption">The world is vast. Most of it remains undiscovered — by you.</p>
     </div>
 
@@ -47,7 +47,7 @@
 
       <a href="natural-world.html" class="card">
         <span class="card-header-bar" style="background:#2d6a2d; height:6px; display:block;"></span>
-        <img src="https://images.unsplash.com/photo-1470071459604-3b5ec3a7fe05?w=500&h=300&fit=crop" alt="A sun-dappled forest" class="card-image">
+        <img src="photos/1470071459604-3b5ec3a7fe05_500x300.jpg" alt="A sun-dappled forest" class="card-image">
         <div class="card-body">
           <img src="img/fern-leaf-vein-pattern.png" alt="" style="max-width:50px; margin-bottom:4px;">
           <div class="card-title">The Natural World</div>
@@ -57,7 +57,7 @@
 
       <a href="inventions.html" class="card">
         <span class="card-header-bar" style="background:#b8860b; height:6px; display:block;"></span>
-        <img src="https://images.unsplash.com/photo-1581093458791-9d42e3c7e117?w=500&h=300&fit=crop" alt="Gears and mechanisms" class="card-image">
+        <img src="photos/photo-1633451238042-85d93d267866_500x300.jpg" alt="Gears and mechanisms" class="card-image">
         <div class="card-body">
           <img src="img/lit-gold-bulb-icon.png" alt="" style="max-width:50px; margin-bottom:4px;">
           <div class="card-title">Inventions &amp; Ideas</div>
@@ -67,7 +67,7 @@
 
       <a href="phenomena.html" class="card">
         <span class="card-header-bar" style="background:#5c2d6e; height:6px; display:block;"></span>
-        <img src="https://images.unsplash.com/photo-1534274988757-a28bf1a57c17?w=500&h=300&fit=crop" alt="Strange northern lights" class="card-image">
+        <img src="photos/1534274988757-a28bf1a57c17_500x300.jpg" alt="Strange northern lights" class="card-image">
         <div class="card-body">
           <img src="img/crystal-rock-gemstone.png" alt="" style="max-width:50px; margin-bottom:4px;">
           <div class="card-title">Strange Phenomena</div>
@@ -77,7 +77,7 @@
 
       <a href="maps.html" class="card">
         <span class="card-header-bar" style="background:#8b4513; height:6px; display:block;"></span>
-        <img src="https://images.unsplash.com/photo-1524661135-423f33e021f6?w=500&h=300&fit=crop" alt="An old map on a weathered table" class="card-image">
+        <img src="photos/photo-1520299607509-dcd935f9a839_500x300.jpg" alt="An old map on a weathered table" class="card-image">
         <div class="card-body">
           <img src="img/world-map-compass-drawing.png" alt="" style="max-width:50px; margin-bottom:4px;">
           <div class="card-title">Maps &amp; Places</div>
@@ -87,7 +87,7 @@
 
       <a href="human-body.html" class="card">
         <span class="card-header-bar" style="background:#a0522d; height:6px; display:block;"></span>
-        <img src="https://images.unsplash.com/photo-1559757175-5700dde675bc?w=500&h=300&fit=crop" alt="An anatomical illustration" class="card-image">
+        <img src="photos/1559757175-5700dde675bc_500x300.jpg" alt="An anatomical illustration" class="card-image">
         <div class="card-body">
           <img src="img/brain-hemisphere-artwork.png" alt="" style="max-width:50px; margin-bottom:4px;">
           <div class="card-title">The Human Body</div>
@@ -97,7 +97,7 @@
 
       <a href="space.html" class="card">
         <span class="card-header-bar" style="background:#1a3a5c; height:6px; display:block;"></span>
-        <img src="https://images.unsplash.com/photo-1462332420958-a05d1e002413?w=500&h=300&fit=crop" alt="A spiral galaxy" class="card-image">
+        <img src="photos/1462332420958-a05d1e002413_500x300.jpg" alt="A spiral galaxy" class="card-image">
         <div class="card-body">
           <img src="img/solar-system-planets-orbit-illustration.png" alt="" style="max-width:50px; margin-bottom:4px;">
           <div class="card-title">Space &amp; Beyond</div>
@@ -116,7 +116,7 @@
 
     <div class="ornament">&sect; &sect; &sect;</div>
 
-    <img src="img/ancient-scroll-with-forest-illustration.png" alt="" class="clipart-divider">
+    <img src="img/ancient-scroll-map-history.png" alt="" class="clipart-divider">
 
     <p class="text-center text-small" style="color:#8b7355; font-style:italic;">
       <span class="easter-egg"> You found something hidden. The world rewards the attentive. </span>
@@ -136,4 +136,4 @@
 
   <script src="js/main.js"></script>
 </body>
-</html>
+</html>