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>

models/TemplateModel.php

@@ -3,9 +3,9 @@
  * TemplateModel - Handles ticket template operations
  */
 class TemplateModel {
-    private $conn;
+    private mysqli $conn;
 
-    public function __construct($conn) {
+    public function __construct(mysqli $conn) {
         $this->conn = $conn;
     }
 
@@ -14,7 +14,7 @@ class TemplateModel {
      *
      * @return array Array of template records
      */
-    public function getAllTemplates() {
+    public function getAllTemplates(): array {
         $sql = "SELECT * FROM ticket_templates WHERE is_active = TRUE ORDER BY template_name";
         $result = $this->conn->query($sql);
 
@@ -31,7 +31,7 @@ class TemplateModel {
      * @param int $templateId Template ID
      * @return array|null Template record or null if not found
      */
-    public function getTemplateById($templateId) {
+    public function getTemplateById(int $templateId): ?array {
         $sql = "SELECT * FROM ticket_templates WHERE template_id = ? AND is_active = TRUE";
         $stmt = $this->conn->prepare($sql);
         $stmt->bind_param("i", $templateId);
@@ -50,7 +50,7 @@ class TemplateModel {
      * @param int $createdBy User ID creating the template
      * @return bool Success status
      */
-    public function createTemplate($data, $createdBy) {
+    public function createTemplate(array $data, int $createdBy): bool {
         $sql = "INSERT INTO ticket_templates (template_name, title_template, description_template,
                 category, type, default_priority, created_by)
                 VALUES (?, ?, ?, ?, ?, ?, ?)";
@@ -77,7 +77,7 @@ class TemplateModel {
      * @param array $data Template data to update
      * @return bool Success status
      */
-    public function updateTemplate($templateId, $data) {
+    public function updateTemplate(int $templateId, array $data): bool {
         $sql = "UPDATE ticket_templates SET
                 template_name = ?,
                 title_template = ?,
@@ -108,7 +108,7 @@ class TemplateModel {
      * @param int $templateId Template ID
      * @return bool Success status
      */
-    public function deactivateTemplate($templateId) {
+    public function deactivateTemplate(int $templateId): bool {
         $sql = "UPDATE ticket_templates SET is_active = FALSE WHERE template_id = ?";
         $stmt = $this->conn->prepare($sql);
         $stmt->bind_param("i", $templateId);