feat(storm-intel): configurable pin radius, fix blank map, 6mo default, remove mock polygons

- Map always renders (removed blank overlay when no nearby events)
- Pin radius is now user-configurable (default 5 mi, input shown in pin strip)
- Default date range changed to 6 months for faster initial load
- IEM fetch window narrowed to 6 months to match default
- MOCK_STORM_EVENTS cleared (IEM provides real NWS polygon data)

src/hooks/useStormEvents.js

@@ -101,7 +101,7 @@ function featureToEvent(feature, idx) {
 
 async function fetchIEMEvents() {
     const now    = new Date();
-    const cutoff = new Date(now.getTime() - 36 * 30.44 * 86400000);
+    const cutoff = new Date(now.getTime() - 6 * 30.44 * 86400000);
     const url    = `${IEM_SBW}?sts=${encodeURIComponent(cutoff.toISOString())}&ets=${encodeURIComponent(now.toISOString())}&wfo=${WFO}`;
 
     const res = await fetch(url);