Add basic authentication to documentation

- Added .htaccess with Apache basic auth configuration
- Created .htpasswd with username 'langmem' and password 'langmem2025'
- Added auth.js for JavaScript-based authentication backup
- Updated all HTML pages to include authentication script
- Added AUTH_INFO.md with access credentials and setup info

Credentials: langmem / langmem2025

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/implementation/index.html

@@ -6,6 +6,7 @@
     <title>Implementation Guide - LangMem Documentation</title>
     <meta name="description" content="Step-by-step implementation guide for building the LangMem long-term memory system with detailed phases and instructions.">
     <link rel="stylesheet" href="../assets/css/style.css">
+    <script src="../auth.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.min.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/prismjs@1.29.0/components/prism-core.min.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/prismjs@1.29.0/plugins/autoloader/prism-autoloader.min.js"></script>