Add detailed AD user statistics script with error handling

[Frafou]

refactor: Overhaul AD user statistics script with comprehensive improvements

MAJOR CHANGES:

• Refactored v1.0.0 to v2.2.0 with significant enhancements

CODE QUALITY IMPROVEMENTS:

• Standardized function names to PascalCase (get-ageindays → Get-AgeInDays)
• Added comprehensive error handling with try-catch blocks throughout
• Implemented proper parameter validation with ValidateNotNullOrEmpty
• Organized code into logical regions (#region Functions, Variables, Main)
• Fixed function call/parameter mismatches and case sensitivity issues
• Removed code duplication and improved reusability

FUNCTIONAL ENHANCEMENTS:

• Automatic output directory creation if it doesn't exist
• Performance optimization: selective AD property queries instead of -Property *
• Proper null handling for PasswordLastSet (returns "Never" instead of errors)
• Added domain auto-detection fallback with error handling
• Module import safety check before loading ActiveDirectory
• Graceful handling of empty AD result sets

ERROR HANDLING & REPORTING:

• Defined exit codes for different error scenarios:
  • 0: Success, 1: Unexpected error, 2: OS incompatible
  • 3: Domain retrieval failed, 4: Directory validation failed
  • 5: User statistics retrieval failed
• Added meaningful error messages with stack traces
• Fixed undefined script variables ($ErrorCount, $WarningCount, $SuccessCount)
• Corrected domain admin count status checking logic

DOCUMENTATION:

• Expanded parameter documentation with types and examples
• Added 4 practical usage examples including -Verbose and -WhatIf variants
• Comprehensive PREREQUISITES section with execution policy guidance
• Detailed HOWTO section with quick start and advanced usage
• Added Exit Codes reference table
• Complete issues fixed changelog for each version
• Multiple LINK references to official Microsoft documentation

OUTPUT & UX:

• Added colored console output for better readability
• Execution time tracking and display
• Improved formatting with headers and separators
• Better status messages with checkmarks and warnings
• Fixed invalid Write-Host -Level parameter issues
• Cleaner, more professional output structure

TECHNICAL FIXES:

• Fixed improper region nesting in try-catch-finally structure
• Removed timestamp expression from default parameter (reliability issue)
• Changed domain admin count error return from 0 to -1 for proper validation
• Fixed OS detection regex pattern (Windows 1* → Windows (10|11|Server))
• Added proper null/empty string handling throughout

BACKWARDS COMPATIBILITY:

• Maintains same parameter names and defaults
• CSV output format unchanged (semicolon-delimited)
• Same column names (Name, AccountAge, PasswordAge)
• Compatible with Windows 10, 11, and Windows Server

VERSION HISTORY:

• v2.0.0: Added comprehensive header (previous release)
• v2.1.0: Corrected function conventions and error handling
• v2.2.0: Fixed remaining issues and refined implementation

TESTING RECOMMENDATIONS:

• Verify on Windows 10, 11, and Windows Server environments
• Test with -Verbose flag for diagnostic output
• Confirm CSV export with different output paths
• Validate against multiple AD domains