Add PHP 7.4+ type hints to helpers, models, and middleware

Added strict typing with parameter types, return types, and property
types across all core classes:
- helpers: Database, ErrorHandler, CacheHelper
- models: TicketModel, UserModel, WorkflowModel, TemplateModel, UserPreferencesModel
- middleware: RateLimitMiddleware, CsrfMiddleware, SecurityHeadersMiddleware

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

helpers/ErrorHandler.php

@@ -6,15 +6,15 @@
  * across the application.
  */
 class ErrorHandler {
-    private static $logFile = null;
-    private static $initialized = false;
+    private static ?string $logFile = null;
+    private static bool $initialized = false;
 
     /**
      * Initialize error handling
      *
      * @param bool $displayErrors Whether to display errors (false in production)
      */
-    public static function init($displayErrors = false) {
+    public static function init(bool $displayErrors = false): void {
         if (self::$initialized) {
             return;
         }
@@ -45,7 +45,7 @@ class ErrorHandler {
      * @param int $errline Line number
      * @return bool
      */
-    public static function handleError($errno, $errstr, $errfile, $errline) {
+    public static function handleError(int $errno, string $errstr, string $errfile, int $errline): bool {
         // Don't handle suppressed errors
         if (!(error_reporting() & $errno)) {
             return false;
@@ -69,7 +69,7 @@ class ErrorHandler {
      *
      * @param Throwable $exception
      */
-    public static function handleException($exception) {
+    public static function handleException(Throwable $exception): void {
         $message = sprintf(
             "Uncaught %s: %s in %s on line %d\nStack trace:\n%s",
             get_class($exception),
@@ -94,7 +94,7 @@ class ErrorHandler {
     /**
      * Handle fatal errors on shutdown
      */
-    public static function handleShutdown() {
+    public static function handleShutdown(): void {
         $error = error_get_last();
 
         if ($error !== null && in_array($error['type'], [E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR])) {
@@ -120,7 +120,7 @@ class ErrorHandler {
      * @param int $level Error level
      * @param array $context Additional context
      */
-    public static function log($message, $level = E_USER_NOTICE, $context = []) {
+    public static function log(string $message, int $level = E_USER_NOTICE, array $context = []): void {
         $timestamp = date('Y-m-d H:i:s');
         $levelName = self::getErrorTypeName($level);
 
@@ -140,7 +140,7 @@ class ErrorHandler {
      * @param int $httpCode HTTP status code
      * @param Throwable|null $exception Original exception (for debug info)
      */
-    public static function sendErrorResponse($message, $httpCode = 500, $exception = null) {
+    public static function sendErrorResponse(string $message, int $httpCode = 500, ?Throwable $exception = null): void {
         http_response_code($httpCode);
 
         if (!headers_sent()) {
@@ -172,7 +172,7 @@ class ErrorHandler {
      * @param array $errors Array of validation errors
      * @param string $message Overall error message
      */
-    public static function sendValidationError($errors, $message = 'Validation failed') {
+    public static function sendValidationError(array $errors, string $message = 'Validation failed'): void {
         http_response_code(422);
 
         if (!headers_sent()) {
@@ -192,7 +192,7 @@ class ErrorHandler {
      *
      * @param string $message Error message
      */
-    public static function sendNotFoundError($message = 'Resource not found') {
+    public static function sendNotFoundError(string $message = 'Resource not found'): void {
         self::sendErrorResponse($message, 404);
     }
 
@@ -201,7 +201,7 @@ class ErrorHandler {
      *
      * @param string $message Error message
      */
-    public static function sendUnauthorizedError($message = 'Authentication required') {
+    public static function sendUnauthorizedError(string $message = 'Authentication required'): void {
         self::sendErrorResponse($message, 401);
     }
 
@@ -210,7 +210,7 @@ class ErrorHandler {
      *
      * @param string $message Error message
      */
-    public static function sendForbiddenError($message = 'Access denied') {
+    public static function sendForbiddenError(string $message = 'Access denied'): void {
         self::sendErrorResponse($message, 403);
     }
 
@@ -220,7 +220,7 @@ class ErrorHandler {
      * @param int $errno Error number
      * @return string Error type name
      */
-    private static function getErrorTypeName($errno) {
+    private static function getErrorTypeName(int $errno): string {
         $types = [
             E_ERROR => 'ERROR',
             E_WARNING => 'WARNING',
@@ -248,7 +248,7 @@ class ErrorHandler {
      * @param int $lines Number of lines to return
      * @return array Log entries
      */
-    public static function getRecentErrors($lines = 50) {
+    public static function getRecentErrors(int $lines = 50): array {
         if (self::$logFile === null || !file_exists(self::$logFile)) {
             return [];
         }