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 />