Align UI with web_template TDS v1.2 standards

- Replace lt-chip priority badges with lt-badge lt-badge-p[1-4] across
  DashboardView, TemplatesView (matches web_template sticky table pattern)
- Add lt-theme-btn theme toggle to header-right; wire lt.theme.toggle()
- Replace ASCII art empty state with lt-empty-state component in dashboard
- Standardize tab wrapper lt-tabs → lt-tab-bar in Dashboard and TicketView
- Add missing lt-keys-help modal to layout_footer (fixes ? key doing nothing)
- Add lt-cmd-overlay command palette container + lt.cmdPalette.init() nav
- Add .lt-timeline-action CSS rule (used in TicketView, was undefined)

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

views/TicketView.php

@@ -266,7 +266,7 @@ include __DIR__ . '/layout_header.php';
 <!-- ═══════════════════════════════════════════════════════════
      TAB NAVIGATION
      ═══════════════════════════════════════════════════════════ -->
-<div class="lt-tabs" role="tablist" aria-label="Ticket content sections">
+<div class="lt-tab-bar" role="tablist" aria-label="Ticket content sections">
   <button type="button" class="lt-tab active" id="description-tab-btn"
           role="tab" data-tab="description-panel" aria-selected="true" aria-controls="description-panel">
     Description