fix: debounce ticker search on Trends page to preserve input focus

The TickerFilter triggered a query on every keystroke, causing re-renders
that stole focus from the input. Now uses a local input state with a
300ms debounce before updating the query, keeping focus on the text box
while typing.

frontend/src/pages/Trends.tsx

@@ -1,7 +1,7 @@
-import { useState } from 'react';
+import { useState, useRef, useEffect } from 'react';
 import { useNavigate, Link } from '@tanstack/react-router';
 import { useTrends, useDocument } from '../api/hooks';
-import { TrendArrow, ConfidenceBar, LoadingSpinner, TickerFilter, Card } from '../components/ui';
+import { TrendArrow, ConfidenceBar, LoadingSpinner, Card } from '../components/ui';
 import type { TrendSummary } from '../api/hooks';
 
 const WINDOWS = ['intraday', '1d', '7d', '30d', '90d'];
@@ -9,8 +9,17 @@ const WINDOWS = ['intraday', '1d', '7d', '30d', '90d'];
 export function TrendsPage() {
   const navigate = useNavigate();
   const [ticker, setTicker] = useState('');
+  const [debouncedTicker, setDebouncedTicker] = useState('');
   const [window, setWindow] = useState<string | undefined>(undefined);
-  const { data, isLoading } = useTrends({ ticker: ticker || undefined, window, limit: 100 });
+  const inputRef = useRef<HTMLInputElement>(null);
+
+  // Debounce ticker search — only query after 300ms of no typing
+  useEffect(() => {
+    const timer = setTimeout(() => setDebouncedTicker(ticker), 300);
+    return () => clearTimeout(timer);
+  }, [ticker]);
+
+  const { data, isLoading } = useTrends({ ticker: debouncedTicker || undefined, window, limit: 100 });
 
   if (isLoading) return <LoadingSpinner />;
 
@@ -19,7 +28,15 @@ export function TrendsPage() {
       <div className="mb-4 flex items-center justify-between">
         <h1 className="text-xl font-semibold text-gray-100">Trends</h1>
         <div className="flex items-center gap-3">
-          <TickerFilter value={ticker} onChange={setTicker} />
+          <input
+            ref={inputRef}
+            type="text"
+            placeholder="Ticker…"
+            value={ticker}
+            onChange={(e) => setTicker(e.target.value.toUpperCase())}
+            className="w-24 rounded-md border border-surface-700 bg-surface-900 px-2 py-1 text-xs text-gray-200 placeholder-gray-500 focus:border-brand-500 focus:outline-none"
+            aria-label="Filter by ticker"
+          />
           <div className="inline-flex rounded-md border border-surface-700" role="group" aria-label="Window selector">
             <button
               onClick={() => setWindow(undefined)}