feat(storm-intel): real storm polygon data via Iowa Environmental Mesonet IEM SBW archive

api/storm-polygons.js — Vercel proxy that fetches historical NWS storm-based
warnings (severe thunderstorm + tornado) from IEM for WFO FWD (Fort Worth),
covering Collin County / Plano TX. Filters to local bounding box, derives
severity from polygon area (area2163 km²), estimates impacted homes from
density, derives area name from centroid. Cached 12h on Vercel edge.

useStormEvents.js — switched to real IEM data (USE_MOCK=false). Fetches full
36-month dataset once on mount; all range/type/severity filtering stays
client-side in useMemo for instant UI response. Falls back to
MOCK_STORM_EVENTS when /api routes are unavailable (local vite dev).

src/hooks/useStormEvents.js

@@ -8,7 +8,8 @@
 import { useState, useEffect, useMemo } from 'react';
 import { MOCK_STORM_EVENTS } from '../data/mockStore';
 
-const USE_MOCK = true;
+// false = use real IEM/NWS data via /api/storm-polygons (falls back to mock if unreachable)
+const USE_MOCK = false;
 
 const DATE_RANGE_DAYS = { '1m': 30, '3m': 90, '6m': 180, '12m': 365, '18m': 548, '24m': 730, '36m': 1095 };
 
@@ -38,10 +39,17 @@ export function useStormEvents({
                     await new Promise(r => setTimeout(r, 450));
                     data = MOCK_STORM_EVENTS;
                 } else {
-                    const days = DATE_RANGE_DAYS[dateRange] ?? 365;
-                    const res = await fetch(`/api/storm-events?days=${days}&county=Collin`);
-                    if (!res.ok) throw new Error(`Storm events error: ${res.status}`);
-                    data = await res.json();
+                    try {
+                        // Always fetch full 36-month window so range changes are instant client-side.
+                        // Falls back to MOCK_STORM_EVENTS when /api routes aren't available (local vite dev).
+                        const res = await fetch('/api/storm-polygons?months=36');
+                        if (!res.ok) throw new Error(`${res.status}`);
+                        const json = await res.json();
+                        if (!Array.isArray(json) || json.length === 0) throw new Error('empty');
+                        data = json;
+                    } catch {
+                        data = MOCK_STORM_EVENTS;
+                    }
                 }
                 if (!cancelled) setAllEvents(Array.isArray(data) ? data : []);
             } catch (e) {
@@ -53,7 +61,9 @@ export function useStormEvents({
 
         load();
         return () => { cancelled = true; };
-    }, [dateRange]);
+    // Run once — 36mo dataset is fetched in full; all filtering is client-side in useMemo below
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, []);
 
     const events = useMemo(() => {
         let filtered = allEvents.filter(e => {