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_INFO.md

@@ -0,0 +1,30 @@
+# LangMem Documentation Authentication
+
+## Access Credentials
+
+The LangMem documentation is protected with basic authentication.
+
+**Username:** `langmem`  
+**Password:** `langmem2025`
+
+## Authentication Methods
+
+### 1. Server-Side (.htaccess)
+- Apache/Nginx basic authentication
+- Uses `.htpasswd` file for credential verification
+- Provides server-level protection
+
+### 2. Client-Side (JavaScript)
+- Backup authentication using browser prompts
+- Session-based authentication
+- Fallback protection if server auth fails
+
+## Files
+- `.htaccess` - Apache authentication configuration
+- `.htpasswd` - Password file (username: langmem)
+- `auth.js` - JavaScript authentication script
+
+## Security Note
+Change the default password for production use by updating both:
+1. `.htpasswd` file (use `htpasswd` command)
+2. `auth.js` file (update hardcoded credentials)