Improve web_template compliance: lt.bytes.format, lt.tableNav, lt.statsFilter

- ticket.js: replace custom formatFileSize() with lt.bytes.format() from web_template base.js; remove the now-redundant local function
- DashboardView.php: add id="tickets-table" and wire lt.tableNav.init() for j/k/Enter keyboard row navigation
- DashboardView.php: add lt-stat-card class + data-filter-key/data-filter-val to open/critical/closed stat cards; wire lt.statsFilter.init() + window.lt_onStatFilter so clicking a stat card filters the ticket list

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

assets/js/ticket.js

@@ -827,7 +827,7 @@ function renderAttachments(attachments) {
                     </a>
                 </div>
                 <div class="attachment-meta">
-                    ${lt.escHtml(att.file_size_formatted || formatFileSize(att.file_size))} • ${lt.escHtml(uploaderName)} • ${uploadDate}
+                    ${lt.escHtml(att.file_size_formatted || lt.bytes.format(att.file_size))} • ${lt.escHtml(uploaderName)} • ${uploadDate}
                 </div>
             </div>
             <div class="attachment-actions">
@@ -841,17 +841,6 @@ function renderAttachments(attachments) {
     container.innerHTML = html;
 }
 
-function formatFileSize(bytes) {
-    if (bytes >= 1073741824) {
-        return (bytes / 1073741824).toFixed(2) + ' GB';
-    } else if (bytes >= 1048576) {
-        return (bytes / 1048576).toFixed(2) + ' MB';
-    } else if (bytes >= 1024) {
-        return (bytes / 1024).toFixed(2) + ' KB';
-    } else {
-        return bytes + ' bytes';
-    }
-}
 
 function deleteAttachment(attachmentId) {
     showConfirmModal(