Integrate web_template design system and fix security/quality issues

Security fixes:
- Add HTTP method validation to delete_comment.php (block CSRF via GET)
- Remove $_GET fallback in comment deletion (was CSRF bypass vector)
- Guard session_start() with session_status() check across API files
- Escape json_encode() data attributes with htmlspecialchars in views
- Escape inline APP_TIMEZONE config values in DashboardView/TicketView
- Validate timezone param against DateTimeZone::listIdentifiers() in index.php
- Remove Database::escape() (was using real_escape_string, not safe)
- Fix AttachmentModel hardcoded connection; inject via constructor

Backend fixes:
- Fix CommentModel bind_param type for ticket_id (s→i)
- Fix buildCommentThread orphan parent guard
- Fix StatsModel JOIN→LEFT JOIN so unassigned tickets aren't excluded
- Add ticket ID validation in BulkOperationsModel before implode()
- Add duplicate key retry in TicketModel::createTicket() for race conditions
- Wrap SavedFiltersModel default filter changes in transactions
- Add null result guards in WorkflowModel query methods

Frontend JS:
- Rewrite toast.js as lt.toast shim (base.js dependency)
- Delegate escapeHtml() to lt.escHtml()
- Rewrite keyboard-shortcuts.js using lt.keys.on()
- Migrate settings.js to lt.api.* and lt.modal.open/close()
- Migrate advanced-search.js to lt.api.* and lt.modal.open/close()
- Migrate dashboard.js fetch calls to lt.api.*; update all dynamic
  modals (bulk ops, quick actions, confirm/input) to lt-modal structure
- Migrate ticket.js fetchMentionUsers to lt.api.get()
- Remove console.log/error/warn calls from JS files

Views:
- Add /web_template/base.css and base.js to all 10 view files
- Call lt.keys.initDefaults() in DashboardView, TicketView, admin views
- Migrate all modal HTML from settings-modal/settings-content to
  lt-modal-overlay/lt-modal/lt-modal-header/lt-modal-body/lt-modal-footer
- Replace style="display:none" with aria-hidden="true" on all modals
- Replace modal open/close style.display with lt.modal.open/close()
- Update modal buttons to lt-btn lt-btn-primary/lt-btn-ghost classes
- Remove manual ESC keydown handlers (replaced by lt.keys.initDefaults)
- Fix unescaped timezone values in TicketView inline script

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

views/TicketView.php

@@ -50,8 +50,10 @@ $nonce = SecurityHeadersMiddleware::getNonce();
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Ticket #<?php echo $ticket['ticket_id']; ?></title>
     <link rel="icon" type="image/png" href="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/images/favicon.png">
+    <link rel="stylesheet" href="/web_template/base.css">
     <link rel="stylesheet" href="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/css/dashboard.css?v=20260131e">
     <link rel="stylesheet" href="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/css/ticket.css?v=20260131e">
+    <script nonce="<?php echo $nonce; ?>" src="/web_template/base.js"></script>
     <script nonce="<?php echo $nonce; ?>" src="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/js/toast.js"></script>
     <script nonce="<?php echo $nonce; ?>" src="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/js/utils.js"></script>
     <script nonce="<?php echo $nonce; ?>" src="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/js/markdown.js?v=20260131e"></script>
@@ -61,9 +63,9 @@ $nonce = SecurityHeadersMiddleware::getNonce();
     // CSRF Token for AJAX requests
     window.CSRF_TOKEN = '<?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 $GLOBALS['config']['TIMEZONE_ABBREV']; ?>';
+    window.APP_TIMEZONE = '<?php echo htmlspecialchars($GLOBALS['config']['TIMEZONE'] ?? 'UTC', ENT_QUOTES, 'UTF-8'); ?>';
+    window.APP_TIMEZONE_OFFSET = <?php echo (int)($GLOBALS['config']['TIMEZONE_OFFSET'] ?? 0); ?>; // minutes from UTC
+    window.APP_TIMEZONE_ABBREV = '<?php echo htmlspecialchars($GLOBALS['config']['TIMEZONE_ABBREV'] ?? 'UTC', ENT_QUOTES, 'UTF-8'); ?>';
     </script>
     <script nonce="<?php echo $nonce; ?>">
     // Store ticket data in a global variable (using json_encode for XSS safety)
@@ -653,15 +655,7 @@ $nonce = SecurityHeadersMiddleware::getNonce();
                 });
             }
 
-            // Settings modal backdrop click
-            var settingsModal = document.getElementById('settingsModal');
-            if (settingsModal) {
-                settingsModal.addEventListener('click', function(e) {
-                    if (e.target.classList.contains('settings-modal')) {
-                        if (typeof closeSettingsModal === 'function') closeSettingsModal();
-                    }
-                });
-            }
+            // Settings modal backdrop click (lt-modal-overlay handles this via data-modal-close)
 
             // Handle change events for data-action
             document.addEventListener('change', function(e) {
@@ -688,17 +682,14 @@ $nonce = SecurityHeadersMiddleware::getNonce();
     </script>
 
     <!-- Settings Modal (same as dashboard) -->
-    <div class="settings-modal" id="settingsModal" style="display: none;" role="dialog" aria-modal="true" aria-labelledby="ticketSettingsTitle">
-        <div class="settings-content">
-            <span class="bottom-left-corner">╚</span>
-            <span class="bottom-right-corner">╝</span>
-
-            <div class="settings-header">
-                <h3 id="ticketSettingsTitle">⚙ System Preferences</h3>
-                <button class="close-settings" id="closeSettingsBtn" aria-label="Close settings">✗</button>
+    <div class="lt-modal-overlay" id="settingsModal" aria-hidden="true" role="dialog" aria-modal="true" aria-labelledby="ticketSettingsTitle">
+        <div class="lt-modal">
+            <div class="lt-modal-header">
+                <span class="lt-modal-title" id="ticketSettingsTitle">⚙ System Preferences</span>
+                <button class="lt-modal-close" data-modal-close aria-label="Close settings">✕</button>
             </div>
 
-            <div class="settings-body">
+            <div class="lt-modal-body">
                 <!-- Display Preferences -->
                 <div class="settings-section">
                     <h4>╔══ Display Preferences ══╗</h4>
@@ -816,13 +807,15 @@ $nonce = SecurityHeadersMiddleware::getNonce();
                 </div>
             </div>
 
-            <div class="settings-footer">
-                <button class="btn btn-primary" id="saveSettingsBtn">Save Preferences</button>
-                <button class="btn btn-secondary" id="cancelSettingsBtn">Cancel</button>
+            <div class="lt-modal-footer">
+                <button class="lt-btn lt-btn-primary" id="saveSettingsBtn">Save Preferences</button>
+                <button class="lt-btn lt-btn-ghost" id="cancelSettingsBtn">Cancel</button>
             </div>
         </div>
     </div>
 
+    <script nonce="<?php echo $nonce; ?>" src="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/js/keyboard-shortcuts.js"></script>
     <script nonce="<?php echo $nonce; ?>" src="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/js/settings.js"></script>
+    <script nonce="<?php echo $nonce; ?>">lt.keys.initDefaults();</script>
 </body>
 </html>