fix: CSRF on ticket create form, DOM-safe duplicate list, audit-log param validation

- TicketController::create: validate csrf_token from POST before processing
- CreateTicketView: emit hidden csrf_token field; replace innerHTML duplicate
  list with DOM methods to prevent any XSS path; guard checkDuplicates() with
  lt.api availability check
- index.php audit-log: allowlist action_type; validate date_from/date_to as
  YYYY-MM-DD before passing to query

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.php

@@ -242,7 +242,9 @@ switch (true) {
         $params = [];
         $types = '';
 
-        if (!empty($_GET['action_type'])) {
+        $allowedActionTypes = ['create','update','delete','comment','assign','status_change','login','security',
+                               'ticket_create','ticket_update','ticket_delete','attachment_delete','attachment_upload'];
+        if (!empty($_GET['action_type']) && in_array($_GET['action_type'], $allowedActionTypes, true)) {
             $whereConditions[] = "al.action_type = ?";
             $params[] = $_GET['action_type'];
             $types .= 's';
@@ -252,15 +254,15 @@ switch (true) {
             $whereConditions[] = "al.user_id = ?";
             $params[] = (int)$_GET['user_id'];
             $types .= 'i';
-            $filters['user_id'] = $_GET['user_id'];
+            $filters['user_id'] = (int)$_GET['user_id'];
         }
-        if (!empty($_GET['date_from'])) {
+        if (!empty($_GET['date_from']) && preg_match('/^\d{4}-\d{2}-\d{2}$/', $_GET['date_from'])) {
             $whereConditions[] = "DATE(al.created_at) >= ?";
             $params[] = $_GET['date_from'];
             $types .= 's';
             $filters['date_from'] = $_GET['date_from'];
         }
-        if (!empty($_GET['date_to'])) {
+        if (!empty($_GET['date_to']) && preg_match('/^\d{4}-\d{2}-\d{2}$/', $_GET['date_to'])) {
             $whereConditions[] = "DATE(al.created_at) <= ?";
             $params[] = $_GET['date_to'];
             $types .= 's';