feat(ui): glowing border pulse for search highlights (#1586)

* feat(ui): add glowing border pulse effect for search highlights

Replace subtle background fade with a 3-pulse blue glow animation
(3s duration) on panels and map countries when navigating via search
or breaking news alerts. Helps users spot the target result.

* fix(map): reset country highlight opacity after pulse animation ends

Without this, fill-opacity decays to near-zero at animation end,
leaving the country nearly invisible until the brief panel closes.

* fix(ui): cancel stale highlight timers and clean up pulse RAF on destroy

- Cancel previous setTimeout before scheduling new highlight, preventing
  premature class removal on rapid re-search (Codex P2)
- Extract shared applyHighlight() in SearchManager with WeakMap tracking
- Cancel countryPulseRaf in DeckGLMap.destroy() to prevent orphaned RAF

* fix(ui): theme-aware highlight opacity and per-element timer tracking

- Use getHighlightRestOpacity() to read current map theme instead of
  hardcoded dark-theme values (0.12), fixing light-theme regression
- Pulse animation base values now scale from theme-correct resting opacity
- BreakingNewsBanner: switch from single timer slot to WeakMap per-element
  tracking, preventing permanent highlight on rapid alert clicks

src/styles/main.css

@@ -10208,19 +10208,36 @@ a.prediction-link:hover {
   border-left-color: var(--accent);
 }
 
-/* Flash highlight animation (for search results) */
-.flash-highlight {
-  animation: flash-highlight 1.5s ease-out;
+/* Search result highlight — glowing border pulse */
+.search-highlight {
+  animation: search-glow-pulse 3s ease-in-out forwards;
 }
 
-@keyframes flash-highlight {
-  0% {
-    background: var(--overlay-heavy);
+@keyframes search-glow-pulse {
+  0%,
+  100% {
+    box-shadow: 0 0 0 0 transparent;
+    border-color: var(--border);
   }
 
-  100% {
-    background: transparent;
+  15%,
+  45%,
+  75% {
+    box-shadow: 0 0 20px 4px #3b82f6, inset 0 0 12px 0 rgba(59, 130, 246, 0.15);
+    border-color: #3b82f6;
   }
+
+  30%,
+  60%,
+  90% {
+    box-shadow: 0 0 6px 1px rgba(59, 130, 246, 0.3);
+    border-color: rgba(59, 130, 246, 0.4);
+  }
+}
+
+/* Legacy alias */
+.flash-highlight {
+  animation: search-glow-pulse 3s ease-in-out forwards;
 }
 
 /* Panel flash when new items arrive */