CSS: extract notification panel inline styles to classes

- lt-notif-empty: replaces all hardcoded padding/font/color/align on
  the empty-state and loading/error text in the notification bell panel
- lt-notif-view-all: replaces width/text-align/display/font-size inline
  style on the 'View dashboard' footer link
- lt-notif-dot: moves border-radius:50%;margin-top from inline style
  (only background color remains inline, which is dynamic per-severity)
- Initial 'Loading…' text in the panel HTML uses lt-notif-empty

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

static/style.css

@@ -124,6 +124,25 @@
 /* ── Search input size variant ───────────────────────────────────── */
 .lt-search-input--sm { width: 180px; }
 
+/* ── Notification panel helpers ──────────────────────────────────── */
+.lt-notif-empty {
+  padding: 1rem;
+  font-size: 0.75rem;
+  color: var(--text-muted);
+  text-align: center;
+}
+.lt-notif-view-all {
+  width: 100%;
+  text-align: center;
+  display: block;
+  font-size: 0.72rem;
+}
+.lt-notif-dot {
+  border-radius: 50%;
+  margin-top: 4px;
+  flex-shrink: 0;
+}
+
 /* ── Divider compact variant ─────────────────────────────────────── */
 .lt-divider--compact { margin: 1rem 0 0.75rem; }