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/auth.js

@@ -0,0 +1,32 @@
+// Simple authentication for LangMem Documentation
+(function() {
+    'use strict';
+    
+    // Check if user is already authenticated
+    if (sessionStorage.getItem('langmem_authenticated') === 'true') {
+        return;
+    }
+    
+    // Simple authentication check
+    function authenticate() {
+        const username = prompt('Username:');
+        const password = prompt('Password:');
+        
+        if (username === 'langmem' && password === 'langmem2025') {
+            sessionStorage.setItem('langmem_authenticated', 'true');
+            return true;
+        } else {
+            alert('Invalid credentials. Access denied.');
+            window.location.href = 'about:blank';
+            return false;
+        }
+    }
+    
+    // Show authentication dialog
+    if (!authenticate()) {
+        // Block access if authentication fails
+        document.addEventListener('DOMContentLoaded', function() {
+            document.body.innerHTML = '<h1>Access Denied</h1><p>Authentication required.</p>';
+        });
+    }
+})();