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/DashboardView.php

@@ -12,7 +12,9 @@ $nonce = SecurityHeadersMiddleware::getNonce();
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Ticket Dashboard</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">
+    <script nonce="<?php echo $nonce; ?>" src="/web_template/base.js"></script>
     <script nonce="<?php echo $nonce; ?>" src="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/js/ascii-banner.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>
@@ -22,12 +24,12 @@ $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>
 </head>
-<body data-categories='<?php echo json_encode($categories); ?>' data-types='<?php echo json_encode($types); ?>'>
+<body data-categories='<?php echo htmlspecialchars(json_encode($categories), ENT_QUOTES, 'UTF-8'); ?>' data-types='<?php echo htmlspecialchars(json_encode($types), ENT_QUOTES, 'UTF-8'); ?>'>
 
     <!-- Terminal Boot Sequence -->
     <div id="boot-sequence" class="boot-overlay">
@@ -573,17 +575,14 @@ $nonce = SecurityHeadersMiddleware::getNonce();
     </section>
 
     <!-- Settings Modal -->
-    <div class="settings-modal" id="settingsModal" style="display: none;" data-action="close-settings-backdrop" role="dialog" aria-modal="true" aria-labelledby="settingsModalTitle">
-        <div class="settings-content">
-            <span class="bottom-left-corner">╚</span>
-            <span class="bottom-right-corner">╝</span>
-
-            <div class="settings-header">
-                <h3 id="settingsModalTitle">⚙ System Preferences</h3>
-                <button class="close-settings" data-action="close-settings" aria-label="Close settings">✗</button>
+    <div class="lt-modal-overlay" id="settingsModal" aria-hidden="true" role="dialog" aria-modal="true" aria-labelledby="settingsModalTitle">
+        <div class="lt-modal">
+            <div class="lt-modal-header">
+                <span class="lt-modal-title" id="settingsModalTitle">⚙ 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>
@@ -724,23 +723,23 @@ $nonce = SecurityHeadersMiddleware::getNonce();
                 </div>
             </div>
 
-            <div class="settings-footer">
-                <button class="btn btn-primary" data-action="save-settings">Save Preferences</button>
-                <button class="btn btn-secondary" data-action="close-settings">Cancel</button>
+            <div class="lt-modal-footer">
+                <button class="lt-btn lt-btn-primary" data-action="save-settings">Save Preferences</button>
+                <button class="lt-btn lt-btn-ghost" data-action="close-settings">Cancel</button>
             </div>
         </div>
     </div>
 
     <!-- Advanced Search Modal -->
-    <div class="settings-modal" id="advancedSearchModal" style="display: none;" data-action="close-advanced-search-backdrop" role="dialog" aria-modal="true" aria-labelledby="advancedSearchModalTitle">
-        <div class="settings-content">
-            <div class="settings-header">
-                <h3 id="advancedSearchModalTitle">🔍 Advanced Search</h3>
-                <button class="close-settings" data-action="close-advanced-search" aria-label="Close advanced search">✗</button>
+    <div class="lt-modal-overlay" id="advancedSearchModal" aria-hidden="true" role="dialog" aria-modal="true" aria-labelledby="advancedSearchModalTitle">
+        <div class="lt-modal">
+            <div class="lt-modal-header">
+                <span class="lt-modal-title" id="advancedSearchModalTitle">🔍 Advanced Search</span>
+                <button class="lt-modal-close" data-modal-close aria-label="Close advanced search">✕</button>
             </div>
 
             <form id="advancedSearchForm">
-                <div class="settings-body">
+                <div class="lt-modal-body">
                     <!-- Saved Filters -->
                     <div class="settings-section">
                         <h4>╔══ Saved Filters ══╗</h4>
@@ -841,10 +840,10 @@ $nonce = SecurityHeadersMiddleware::getNonce();
                     </div>
                 </div>
 
-                <div class="settings-footer">
-                    <button type="submit" class="btn btn-primary">Search</button>
-                    <button type="button" class="btn btn-secondary" data-action="reset-advanced-search">Reset</button>
-                    <button type="button" class="btn btn-secondary" data-action="close-advanced-search">Cancel</button>
+                <div class="lt-modal-footer">
+                    <button type="submit" class="lt-btn lt-btn-primary">Search</button>
+                    <button type="button" class="lt-btn lt-btn-ghost" data-action="reset-advanced-search">Reset</button>
+                    <button type="button" class="lt-btn lt-btn-ghost" data-action="close-advanced-search">Cancel</button>
                 </div>
             </form>
         </div>
@@ -854,6 +853,8 @@ $nonce = SecurityHeadersMiddleware::getNonce();
     <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/advanced-search.js"></script>
     <script nonce="<?php echo $nonce; ?>">
+        // Initialize lt keyboard defaults (ESC closes modals, Ctrl+K focuses search, ? shows help)
+        lt.keys.initDefaults();
         // Event delegation for all data-action handlers
         document.addEventListener('click', function(event) {
             const target = event.target.closest('[data-action]');
@@ -882,10 +883,6 @@ $nonce = SecurityHeadersMiddleware::getNonce();
                     closeSettingsModal();
                     break;
 
-                case 'close-settings-backdrop':
-                    if (event.target === target) closeSettingsModal();
-                    break;
-
                 case 'save-settings':
                     saveSettings();
                     break;
@@ -906,10 +903,6 @@ $nonce = SecurityHeadersMiddleware::getNonce();
                     closeAdvancedSearch();
                     break;
 
-                case 'close-advanced-search-backdrop':
-                    if (event.target === target) closeAdvancedSearch();
-                    break;
-
                 case 'reset-advanced-search':
                     resetAdvancedSearch();
                     break;