feat: Add timezone support with EST default

- Add TIMEZONE config option (default: America/New_York)
- Set PHP default timezone from config
- Add timezone offset and abbreviation for JavaScript
- Update stat card filters to use server timezone
- Add timezone config to Dashboard and Ticket views

Timezone can be changed via TIMEZONE env variable.
All dates now consistent with server timezone (EST by default).

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

views/TicketView.php

@@ -58,6 +58,10 @@ function formatDetails($details, $actionType) {
         require_once __DIR__ . '/../middleware/CsrfMiddleware.php';
         echo CsrfMiddleware::getToken();
     ?>';
+    // Timezone configuration (from server)
+    window.APP_TIMEZONE = '<?php echo $GLOBALS['config']['TIMEZONE']; ?>';
+    window.APP_TIMEZONE_OFFSET = <?php echo $GLOBALS['config']['TIMEZONE_OFFSET']; ?>; // minutes from UTC
+    window.APP_TIMEZONE_ABBREV = '<?php echo $GLOBALS['config']['TIMEZONE_ABBREV']; ?>';
     </script>
     <script>
     // Store ticket data in a global variable