feat: themed avatars and branding updates (#67)

## Summary

Added comprehensive avatar and branding updates across the library application:

### 🌸 Updated Main Branding
- New library-themed avatar (with playful "shh" gesture) for navigation icon
- Updated favicon and all PWA icons (10 sizes from 72x72 to 512x512)
- Added hero avatar to home page between title and subtitle
- All branding uses consistent circular styling with elegant hover effects

### 🎨 Media-Specific Avatars
Added unique themed avatars to each media list page:

- **🎮 Games**: Gaming setup with controller and LED lights (red #ff6b6b border)
- **📚 Books**: Reading in cozy library setting (brown #8b6f47 border)
- **🎵 Music**: Joyful with headphones and urban nightscape (blue #74b9ff border)
- **📺 Shows**: Relaxing with remote and theater curtains (pink #e84393 border)
- **📖 Manga**: Reading manga with shelves background (teal #00b894 border)
- **🎨 Art**: Art studio with paintbrush (yellow #fdcb6e border)

### ✨ Features
- 120x120px circular avatars with themed colour borders
- Smooth hover animations (scale + shadow effects)
- Centered hero sections at top of each list view
- Consistent styling across all media types
- Perfect integration with existing colour themes

### 📊 Technical Details
- All icons generated from source images at multiple resolutions
- Static assets served with correct MIME types
- Optimised image formats for performance
- Responsive design with proper accessibility attributes

## Test Plan

- [x] Verify navigation icon displays correctly in header
- [x] Check favicon appears in browser tabs
- [x] Test PWA icons on mobile devices
- [x] Confirm home page hero avatar renders properly
- [x] Verify all 6 media list avatars display with correct borders
- [x] Test hover animations on all avatars
- [x] Verify build succeeds
- [x] Check static assets serve with correct MIME types

🌸 Created with love by Hikari 💖

Reviewed-on: #67
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

apps/frontend/src/app/components/art/art-gallery.component.ts

@@ -23,6 +23,10 @@ import { Art, CreateArtDto, UpdateArtDto, Comment, SuggestionEntity, Link } from
   imports: [CommonModule, FormsModule, RouterModule, PaginationComponent, LikeButtonComponent],
   template: `
     <div class="container">
+      <div class="page-hero">
+        <img src="/assets/avatars/art-avatar.jpg" alt="Art avatar" class="page-avatar" />
+      </div>
+
       <div class="header-section">
         <h2>Art Gallery</h2>
         <p class="subtitle">Artwork of Naomi</p>
@@ -458,6 +462,26 @@ import { Art, CreateArtDto, UpdateArtDto, Comment, SuggestionEntity, Link } from
       padding: 2rem;
     }
 
+    .page-hero {
+      text-align: center;
+      margin-bottom: 2rem;
+    }
+
+    .page-avatar {
+      width: 120px;
+      height: 120px;
+      border-radius: 50%;
+      object-fit: cover;
+      border: 3px solid #fdcb6e;
+      box-shadow: 0 4px 12px rgba(253, 203, 110, 0.3);
+      transition: all 0.3s;
+    }
+
+    .page-avatar:hover {
+      transform: scale(1.05);
+      box-shadow: 0 8px 16px rgba(253, 203, 110, 0.5);
+    }
+
     .header-section {
       display: flex;
       flex-direction: column;