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>

backend/routers/market_events.py

@@ -171,7 +171,13 @@ def list_events(
     # When joining with instrument_impacts an event can appear multiple times — use GROUP BY
     group_sql = "GROUP BY me.id" if instrument else ""
 
-    # Extra column: best instrument score for display
+    # Extra columns: evaluated flag + optional instrument score
+    evaluated_col = (
+        ", (CASE WHEN EXISTS ("
+        "SELECT 1 FROM instrument_impacts _ei "
+        "WHERE _ei.source_type='event' AND _ei.source_id=me.id"
+        ") THEN 1 ELSE 0 END) as evaluated"
+    )
     inst_col = (
         ", MAX(COALESCE(ii.adjusted_score, ii.impact_score)) as inst_score"
         ", ii.direction as inst_direction"
@@ -181,7 +187,7 @@ def list_events(
         SELECT COUNT(DISTINCT me.id) FROM market_events me {join_clause} {where_sql}
     """
     data_sql = f"""
-        SELECT me.* {inst_col}
+        SELECT me.* {evaluated_col} {inst_col}
         FROM market_events me {join_clause}
         {where_sql} {group_sql} {order_sql}
         LIMIT ? OFFSET ?