Add book catalog example with global/local template system

Features:
- Global template configuration (sqlite_global_templates directive)
- Template path resolution relative to location
- Automatic template loading from directories
- Local templates override global templates
- Content handler installation via directive setter

Book Catalog Example:
- Complete working example with 10 technical books
- SQLite database with setup script
- 4 browseable pages (all, programming, databases, computer-science)
- Shared global templates (header, footer, book_card partial)
- Category-specific local templates with unique theming
- Responsive gradient UI design
- Working navigation and filtering

Configuration:
- sqlite_global_templates: HTTP main-level directive for shared templates
- sqlite_template: Location-level directive (sets content handler)
- Template resolution: {doc_root}{uri}/{template_name}
- All .hbs files in directories auto-loaded as partials

Technical improvements:
- Fixed content handler setup (not phase handler)
- Proper HttpModuleMainConf and HttpModuleLocationConf traits
- Template directory scanning and registration
- Error handling with debug logging

server_root/global_templates/book_card.hbs

@@ -0,0 +1,16 @@
+<div class="book-card">
+    <div class="book-header">
+        <h3 class="book-title">{{title}}</h3>
+        <div class="book-rating">⭐ {{rating}}</div>
+    </div>
+    <p class="book-author">by {{author}}</p>
+    <p class="book-description">{{description}}</p>
+    <div class="book-details">
+        <span class="book-genre">{{genre}}</span>
+        <span class="book-year">{{year}}</span>
+        {{#if isbn}}
+        <span class="book-isbn">ISBN: {{isbn}}</span>
+        {{/if}}
+    </div>
+</div>
+