feat(site): Add hero imagery and enhance visual design with background images

- Replace gradient backgrounds with high-quality imagery for hero and page sections
- Add 10 new pet care and team member photos (hero, services, team profiles)
- Implement overlay system for hero sections with improved text contrast and readability
- Restructure hero markup with overlay div and hero-content wrapper for proper layering
- Convert about preview section to two-column grid layout with image and content
- Update footer credits to include photo attribution to Unsplash
- Enhance dark mode styling for hero sections with adjusted overlay gradients
- Add responsive grid layout for about section that stacks on mobile devices
- Improve visual hierarchy and brand presentation across all pages

index.html

@@ -33,7 +33,8 @@
     <main class="site-main">
         <!-- Hero Section -->
         <section class="hero" aria-labelledby="hero-heading">
-            <div class="container">
+            <div class="hero-overlay"></div>
+            <div class="container hero-content">
                 <p class="hero-emoji" aria-hidden="true">🐾</p>
                 <h1 id="hero-heading">Your Dog Deserves the Best Day Ever</h1>
                 <p class="hero-subheadline">Trusted dog walking, grooming, and overnight care from people who truly love dogs.</p>
@@ -78,9 +79,16 @@
         <!-- About Preview -->
         <section class="about-preview" aria-labelledby="about-preview-heading">
             <div class="container">
-                <h2 id="about-preview-heading" class="section-title">Meet the Team</h2>
-                <p class="about-preview-text">We are a small crew of dog lovers dedicated to keeping your pups happy and healthy. Every handler on our team is certified and genuinely passionate about dogs.</p>
-                <a href="/about.html" class="btn btn-secondary">Learn About Us</a>
+                <div class="about-preview-grid">
+                    <div class="about-preview-image">
+                        <img src="images/dog-walking.jpg" alt="Happy dog being walked through a sunny neighborhood" loading="lazy">
+                    </div>
+                    <div class="about-preview-content">
+                        <h2 id="about-preview-heading" class="section-title">Meet the Team</h2>
+                        <p class="about-preview-text">We are a small crew of dog lovers dedicated to keeping your pups happy and healthy. Every handler on our team is certified and genuinely passionate about dogs.</p>
+                        <a href="/about.html" class="btn btn-secondary">Learn About Us</a>
+                    </div>
+                </div>
             </div>
         </section>
 
@@ -143,7 +151,7 @@
             </div>
             <div class="footer-bottom">
                 <p>&copy; 2026 Happy Tails Pet Care. All rights reserved.</p>
-                <p class="footer-credits">Hosted by <a href="https://sloanops.com" target="_blank" rel="noopener">SloanOps</a></p>
+                <p class="footer-credits">Hosted by <a href="https://sloanops.com" target="_blank" rel="noopener">SloanOps</a> · Photos by <a href="https://unsplash.com" target="_blank" rel="noopener">Unsplash</a></p>
             </div>
         </div>
     </footer>