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/.htaccess

@@ -0,0 +1,4 @@
+AuthType Basic
+AuthName "LangMem Documentation - Restricted Access"
+AuthUserFile /home/klas/langmem/docs/.htpasswd
+Require valid-user