fix(helpdesk): consolidation fixes from drift/performance/security review

- Fix docblock: getTicketsForTeam() uses PBI_FP_Tickets, not LV
- Process_Stage check now uses isset() guard — FP entity does not
  expose this field, prevents false positives from default 0
- Remove exception message from JSON error response (security)
- Remove dead JS functions: formatAge(), formatDate()
- Remove debug console.error and verbose error display from JS

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/helpdesk/lib/Module/Helpdesk/Service/DebitorDetailService.php

@@ -1603,8 +1603,10 @@ class DebitorDetailService
 
         foreach ($tickets as $ticket) {
             $state = trim((string) ($ticket['Ticket_State'] ?? ''));
+            // Team query uses PBI_FP_Tickets which has no Process_Stage;
+            // fall back to Process_Stage only when present (LV entity).
             $isClosed = self::isClosedTicketState($state)
-                || (int) ($ticket['Process_Stage'] ?? 0) === 40;
+                || (isset($ticket['Process_Stage']) && (int) $ticket['Process_Stage'] === 40);
 
             $rawUser = trim((string) ($ticket['Support_User_Name'] ?? ''));
             $normalizedUser = $rawUser === '' ? '' : strtolower($rawUser);