Add stat cards, lt-frame alert queue, and timeline for resolved alerts

- Four lt-stat-card widgets (Critical, Warning, Hosts, Resolved 24h)
  below the status bar; Critical card pulses red when count > 0
- Clicking Critical or Warning card filters the events table by severity
- Events table wrapped in lt-frame with ASCII corner ornaments and
  lt-section-header; filter bar moved to lt-toolbar with lt-search icon
- Recently Resolved table replaced with lt-timeline component
- updateStatusBar() and updateHostGrid() keep stat card values live

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

static/style.css

@@ -995,6 +995,17 @@
 .diag-pulse-link a { color: var(--cyan); }
 .diag-pulse-link a:hover { text-shadow: var(--glow-cyan); }
 
+/* ── Stat card alert variant (pulsing border when critical > 0) ─── */
+.lt-stat-card--alert {
+  border-color: var(--red) !important;
+  box-shadow: 0 0 8px rgba(255,45,85,.25) !important;
+  animation: topo-pulse-down 2s ease-in-out infinite;
+}
+.lt-stat-card--alert::before { background: var(--red); box-shadow: var(--glow-red); }
+
+/* ── lt-frame inside g-section: no extra bottom margin ────────────── */
+.g-section > .lt-frame { margin-bottom: 0; }
+
 /* ── Responsive ───────────────────────────────────────────────────── */
 @media (max-width: 768px) {
   .host-grid         { grid-template-columns: 1fr; }