Add admin console with login, dashboard, content/config/plugin/user management

File-based admin panel accessible at /admin.php with:
- Session-based auth with bcrypt hashing and brute-force protection
- Dashboard with site statistics and quick actions
- Content manager: browse, create, edit, delete files
- Config editor with JSON validation
- Plugin overview with status indicators
- User management: add, remove, change passwords
- CSRF protection on all forms, path traversal prevention
- Updated README (NL/EN) and guides with admin documentation

README.en.md

@@ -17,6 +17,7 @@ A lightweight, file-based content management system built with PHP.
 - ⚙️ **JSON Configuration** - Easy configuration via JSON
 - 🎨 **Bootstrap 5** - Modern UI framework
 - 🔒 **Security** - Secure content management (100/100 security score)
+- 🛡️ **Admin Console** - Built-in admin panel for content, config, plugins and user management
 
 ## 🚀 Quick Start
 
@@ -47,6 +48,13 @@ codepress/
 │       ├── markdown_content.mustache
 │       ├── php_content.mustache
 │       └── html_content.mustache
+├── admin-console/                  # Admin panel
+│   ├── config/
+│   │   ├── app.php                # Admin configuration
+│   │   └── admin.json             # Users & security
+│   ├── src/
+│   │   └── AdminAuth.php          # Authentication service
+│   └── templates/                  # Admin templates
 ├── public/                         # Web root
 │   ├── assets/
 │   │   ├── css/
@@ -56,7 +64,8 @@ codepress/
 │   │   ├── nl.homepage.md          # Dutch homepage
 │   │   ├── en.homepage.md          # English homepage
 │   │   └── [lang].[page].md        # Multi-language pages
-│   └── index.php                   # Entry point
+│   ├── index.php                   # Website entry point
+│   └── admin.php                   # Admin entry point
 ├── config.json                     # Configuration
 ├── version.php                     # Version tracking
 └── README.md                       # This file
@@ -315,6 +324,28 @@ See [pentest/PENTEST.md](pentest/PENTEST.md) for detailed security report.
 
 See [function-test/test-report.md](function-test/test-report.md) for detailed test results.
 
+## 🛡️ Admin Console
+
+CodePress includes a built-in admin panel for managing your website.
+
+**Access:** `/admin.php` | **Default login:** `admin` / `admin`
+
+### Modules
+- **Dashboard** - Overview with statistics and quick actions
+- **Content** - Browse, create, edit and delete files
+- **Configuration** - Edit `config.json` with JSON validation
+- **Plugins** - Overview of installed plugins
+- **Users** - Add, remove users and change passwords
+
+### Security
+- Session-based authentication with bcrypt password hashing
+- CSRF protection on all forms
+- Brute-force protection (5 attempts, 15 min lockout)
+- Path traversal protection
+- Session timeout (30 min)
+
+> **Important:** Change the default password immediately after installation via Users.
+
 ## 📖 Documentation
 
 - **[Guide (NL)](guide/nl.codepress.md)** - Dutch documentation