Fix API security: dependency/visibility leaks, authz, CSRF, comment spoofing

- ticket_dependencies.php: pass current user id/groups/is_admin into the
  visibility-filtered DependencyModel methods; drop (int) casts that
  stripped leading zeros from varchar ticket_ids
- update_ticket.php: authorize visibility changes (admin or creator only);
  enforce requires_comment transitions server-side (400 + requires_comment
  flag so the client can prompt-and-retry); return proper 401/400/403
- add_comment.php: take commenter name from the session not the client
  (anti-spoofing); validate parent_comment_id belongs to the ticket;
  reject empty comments; pass ticket visibility to notifications so
  non-public comment bodies aren't leaked
- add_comment/update_comment/bulk_operation: validate CSRF for all
  state-changing methods, not just POST
- bootstrap.php: return the current CSRF token on rejection and never
  rotate it on a rejected request, so a desynced client can auto-recover
- correct auth->401 and validation->400 status codes across these endpoints

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

api/bulk_operation.php

@@ -19,9 +19,9 @@ if (!isset($_SESSION['user']) || !isset($_SESSION['user']['user_id'])) {
     exit;
 }
 
-// CSRF Protection
+// CSRF Protection for all state-changing methods (any non-GET/HEAD request)
 require_once dirname(__DIR__) . '/middleware/CsrfMiddleware.php';
-if ($_SERVER['REQUEST_METHOD'] === 'POST') {
+if (!in_array($_SERVER['REQUEST_METHOD'], ['GET', 'HEAD'], true)) {
     $csrfToken = $_SERVER['HTTP_X_CSRF_TOKEN'] ?? '';
     if (!CsrfMiddleware::validateToken($csrfToken)) {
         http_response_code(403);
@@ -47,6 +47,7 @@ $parameters = $data['parameters'] ?? null;
 // Validate input
 $validOperationTypes = ['bulk_close', 'bulk_assign', 'bulk_priority', 'bulk_status', 'bulk_delete'];
 if (!$operationType || !in_array($operationType, $validOperationTypes, true) || empty($ticketIds)) {
+    http_response_code(400);
     echo json_encode(['success' => false, 'error' => 'Operation type and ticket IDs required']);
     exit;
 }
@@ -57,6 +58,7 @@ $ticketIds = array_values(array_filter(array_map(function ($id) {
     return (ctype_digit($s) && (int)$s > 0) ? $s : null;
 }, $ticketIds)));
 if (empty($ticketIds)) {
+    http_response_code(400);
     echo json_encode(['success' => false, 'error' => 'No valid ticket IDs provided']);
     exit;
 }