feat: Add comprehensive documentation suite and reorganize project structure

- Created complete documentation in docs/ directory
- Added PROJECT_OVERVIEW.md with feature highlights and getting started guide
- Added ARCHITECTURE.md with system design and technical details
- Added SECURITY.md with comprehensive security implementation guide
- Added DEVELOPMENT.md with development workflows and best practices
- Added DEPLOYMENT.md with production deployment instructions
- Added API.md with complete REST API documentation
- Added CONTRIBUTING.md with contribution guidelines
- Added CHANGELOG.md with version history and migration notes
- Reorganized all documentation files into docs/ directory for better organization
- Updated README.md with proper documentation links and quick navigation
- Enhanced project structure with professional documentation standards

Zend/Gdata/Books/Extension/ThumbnailLink.php

@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * Zend Framework
+ *
+ * LICENSE
+ *
+ * This source file is subject to the new BSD license that is bundled
+ * with this package in the file LICENSE.txt.
+ * It is also available through the world-wide-web at this URL:
+ * http://framework.zend.com/license/new-bsd
+ * If you did not receive a copy of the license and are unable to
+ * obtain it through the world-wide-web, please send an email
+ * to license@zend.com so we can send you a copy immediately.
+ *
+ * @category   Zend
+ * @package    Zend_Gdata
+ * @subpackage Books
+ * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license    http://framework.zend.com/license/new-bsd     New BSD License
+ * @version    $Id: ThumbnailLink.php 24594 2012-01-05 21:27:01Z matthew $
+ */
+
+/**
+ * @see Zend_Gdata_Books_Extension_BooksLink
+ */
+require_once 'Zend/Gdata/Books/Extension/BooksLink.php';
+
+/**
+ * Describes a thumbnail link
+ *
+ * @category   Zend
+ * @package    Zend_Gdata
+ * @subpackage Books
+ * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license    http://framework.zend.com/license/new-bsd     New BSD License
+ */
+class Zend_Gdata_Books_Extension_ThumbnailLink extends
+    Zend_Gdata_Books_Extension_BooksLink
+{
+
+    /**
+     * Constructor for Zend_Gdata_Books_Extension_ThumbnailLink which
+     * Describes a thumbnail link
+     *
+     * @param string|null $href Linked resource URI
+     * @param string|null $rel Forward relationship
+     * @param string|null $type Resource MIME type
+     * @param string|null $hrefLang Resource language
+     * @param string|null $title Human-readable resource title
+     * @param string|null $length Resource length in octets
+     */
+    public function __construct($href = null, $rel = null, $type = null,
+            $hrefLang = null, $title = null, $length = null)
+    {
+        $this->registerAllNamespaces(Zend_Gdata_Books::$namespaces);
+        parent::__construct($href, $rel, $type, $hrefLang, $title, $length);
+    }
+
+}