feat: Add comprehensive configuration system and examples

Added complete configuration support with multiple formats and examples
to help users easily configure py-wikijs for their projects.

New Features:
- Configuration file templates for ENV, YAML, JSON, and INI formats
- config_helper.py: Universal configuration loader and client factory
  * Auto-detects and loads configs from multiple formats
  * Supports environment variables, YAML, JSON, and INI files
  * Provides create_client_from_config() for easy client creation
  * Validates configuration and provides helpful error messages

Configuration Templates:
- config.env.example: Environment variables (Docker, 12-factor apps)
- config.yaml.example: YAML with multi-environment support
- config.json.example: JSON for programmatic configuration
- config.ini.example: INI for traditional setups

Usage Examples:
- using_env_config.py: Complete example using .env files
- using_yaml_config.py: Complete example using YAML configuration
- using_json_config.py: Complete example using JSON configuration

Documentation:
- docs/CONFIGURATION_GUIDE.md: Comprehensive configuration guide
  * All configuration methods explained
  * Security best practices
  * Environment-specific configurations
  * Troubleshooting guide

Benefits:
✅ Flexible configuration (choose your preferred format)
✅ Keep credentials secure (no hardcoding)
✅ Environment-specific configs (dev/staging/prod)
✅ Docker/container-ready
✅ Full validation and error handling
✅ Comprehensive documentation and examples

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

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

examples/using_json_config.py

@@ -0,0 +1,108 @@
+#!/usr/bin/env python3
+"""Example: Using JSON configuration file with py-wikijs.
+
+This example shows how to use a JSON configuration file to configure
+the WikiJS client.
+
+Setup:
+    1. Copy config.json.example to config.json
+    2. Update config.json with your Wiki.js credentials
+    3. Run this script
+
+Usage:
+    python using_json_config.py
+"""
+
+import json
+import sys
+from pathlib import Path
+
+# Add examples directory to path
+sys.path.insert(0, str(Path(__file__).parent))
+
+from config_helper import create_client_from_config, load_config
+
+
+def main():
+    """Main function."""
+    print("=" * 60)
+    print("Using JSON Configuration with py-wikijs")
+    print("=" * 60)
+
+    json_file = Path(__file__).parent / "config.json"
+
+    if not json_file.exists():
+        print(f"\n⚠️  config.json not found at {json_file}")
+        print("   Copy config.json.example to config.json and update it")
+        return 1
+
+    try:
+        # Load configuration
+        print("\n📁 Loading configuration from config.json...")
+        config = load_config(json_file)
+        print("✅ Configuration loaded successfully")
+
+        # Pretty print config (without sensitive data)
+        safe_config = config.copy()
+        if "wikijs" in safe_config and "auth" in safe_config["wikijs"]:
+            if "api_key" in safe_config["wikijs"]["auth"]:
+                safe_config["wikijs"]["auth"]["api_key"] = "***REDACTED***"
+
+        print(f"\nConfiguration (sanitized):")
+        print(json.dumps(safe_config, indent=2))
+
+        # Create client
+        print("\n🔌 Creating WikiJS client...")
+        client = create_client_from_config(config)
+        print(f"✅ Client created successfully")
+
+        # Test connection
+        print("\n🔍 Testing connection...")
+        pages = client.pages.list()
+        print(f"✅ Connected! Found {len(pages)} page(s)")
+
+        # Create a new page (example)
+        if input("\n❓ Create a test page? (y/N): ").lower() == "y":
+            from wikijs.models import PageCreate
+
+            test_page = PageCreate(
+                title="Test Page from JSON Config",
+                path="test/json-config-example",
+                content="# Test Page\n\nCreated using JSON configuration!",
+                description="Example page created from JSON config",
+                is_published=False,
+                locale="en",
+                tags=["test", "json", "config"],
+            )
+
+            print("\n📝 Creating test page...")
+            created = client.pages.create(test_page)
+            print(f"✅ Page created: {created.title} (ID: {created.id})")
+            print(f"   Path: {created.path}")
+
+        # Show metrics
+        metrics = client.get_metrics()
+        print(f"\n📊 Client Metrics:")
+        print(f"   Total requests: {metrics['total_requests']}")
+        print(f"   Successful: {metrics['successful_requests']}")
+        print(f"   Failed: {metrics['failed_requests']}")
+
+    except FileNotFoundError as e:
+        print(f"❌ {e}")
+        return 1
+
+    except Exception as e:
+        print(f"❌ Error: {e}")
+        import traceback
+
+        traceback.print_exc()
+        return 1
+
+    print("\n" + "=" * 60)
+    print("✅ Example completed successfully!")
+    print("=" * 60)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())