fix: evaluated field on event list + abort race condition

- Backend: add evaluated subquery column to list SELECT so each event
  returns evaluated=1/0 (was missing, causing all events to appear
  as unevaluated regardless of filter)
- Frontend: AbortController cancels the previous in-flight fetch when
  a new load fires, preventing stale results from overwriting current
  filter state

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

frontend/src/pages/MarketEvents.tsx

@@ -1173,9 +1173,15 @@ export default function MarketEvents() {
     setDateTo(to)
   }, [])
 
-  const debounceRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const debounceRef  = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const abortRef     = useRef<AbortController | null>(null)
 
   const load = useCallback(async () => {
+    // Cancel any in-flight fetch
+    abortRef.current?.abort()
+    abortRef.current = new AbortController()
+    const signal = abortRef.current.signal
+
     setLoading(true)
     const params = new URLSearchParams()
     if (search)    params.set('search', search)
@@ -1193,11 +1199,15 @@ export default function MarketEvents() {
     params.set('sort_by',  instTicker ? 'instrument_score' : sortBy)
     params.set('sort_dir', sortDir)
     params.set('limit', '500')
-    const r = await fetch(`/api/market-events?${params}`)
-    if (r.ok) {
-      const d = await r.json()
-      setEvents(d.events)
-      setTotal(d.total)
+    try {
+      const r = await fetch(`/api/market-events?${params}`, { signal })
+      if (r.ok) {
+        const d = await r.json()
+        setEvents(d.events)
+        setTotal(d.total)
+      }
+    } catch (e: any) {
+      if (e.name === 'AbortError') return  // superseded by a newer load
     }
     setLoading(false)
   }, [search, category, level, minScore, dateFrom, dateTo, evaluated,