fix: show TA-lib pattern spans on chart and add delete all annotations button

- Fix SpanAnnotationManager price range calculation: use direct candle
  filtering by time range instead of dummy Candle objects that fell back
  to 0/0 high/low, causing invisible rectangles
- Add handleDeleteAllAnnotations in page.tsx (deletes all span annotations
  and regular annotations for current chart)
- Add 'Delete All Annotations' button in sidebar below TA-Lib panel

src/app/page.tsx

@@ -405,6 +405,21 @@ export default function Home() {
     }
   };
 
+  const handleDeleteAllAnnotations = async () => {
+    if (!activeChartId) return;
+    await Promise.all([
+      fetch(`/api/span-annotations?chartId=${activeChartId}`, { method: 'DELETE' }),
+      fetch(`/api/annotations?all=true&chartId=${activeChartId}`, { method: 'DELETE' }),
+    ]);
+    await Promise.all([
+      fetchSpanAnnotations(activeChartId),
+      fetchAnnotations(activeChartId),
+      chartRef.current?.refreshData(),
+    ]);
+    setSelectedSpanId(null);
+    setSelectedLabelId(null);
+  };
+
   const handleLabelDelete = async (id: number) => {
     setAnnotations(annotations.filter((a) => a.id !== id));
     if (selectedLabelId === id) {
@@ -778,6 +793,17 @@ export default function Home() {
           />
         </div>
 
+        {/* Delete all annotations */}
+        <div className="px-3 py-2 border-t border-sidebar-border">
+          <button
+            onClick={handleDeleteAllAnnotations}
+            disabled={!activeChartId}
+            className="w-full px-2 py-1 text-[10px] text-destructive border border-destructive/30 rounded hover:bg-destructive/10 transition-colors disabled:opacity-50"
+          >
+            Delete All Annotations
+          </button>
+        </div>
+
         {/* Training Panel */}
         <div className="px-3 py-2 border-t border-sidebar-border">
           <TrainingPanel />

src/components/SpanAnnotationManager.tsx

@@ -112,12 +112,31 @@ export default function SpanAnnotationManager({
 
     // Create primitives for each span annotation
     spanAnnotations.forEach((span) => {
-      const { max_high, min_low } = calculatePriceRange(
-        { time: span.start_time, open: 0, high: 0, low: 0, close: 0 },
-        { time: span.end_time, open: 0, high: 0, low: 0, close: 0 }
+      // Find candles within span time range for price calculation
+      const spanCandles = candles.filter(
+        (c) => c.time >= span.start_time && c.time <= span.end_time
       );
+      let max_high: number;
+      let min_low: number;
+      if (spanCandles.length > 0) {
+        max_high = Math.max(...spanCandles.map((c) => c.high));
+        min_low = Math.min(...spanCandles.map((c) => c.low));
+      } else {
+        // Fallback: find nearest candles to span boundaries
+        const nearest = candles.reduce(
+          (acc, c) => {
+            const distStart = Math.abs(c.time - span.start_time);
+            const distEnd = Math.abs(c.time - span.end_time);
+            if (distStart < acc.startDist) acc = { ...acc, startCandle: c, startDist: distStart };
+            if (distEnd < acc.endDist) acc = { ...acc, endCandle: c, endDist: distEnd };
+            return acc;
+          },
+          { startCandle: candles[0], startDist: Infinity, endCandle: candles[0], endDist: Infinity }
+        );
+        max_high = Math.max(nearest.startCandle?.high ?? 0, nearest.endCandle?.high ?? 0);
+        min_low = Math.min(nearest.startCandle?.low ?? 0, nearest.endCandle?.low ?? 0);
+      }
 
-      // If we can't calculate price range from candles, use sensible defaults
       const spanData: SpanData = {
         id: span.id,
         start_time: span.start_time,