fix: Ctrl+S in SECTION-TAB exports SF instead of saving section

First Ctrl+S handler (line 8066, handleExportSFS) catches
ALL Ctrl+S before second handler (line 8157, save section)
ever runs. Moved section-tab check into first handler:
activeTab.startsWith('session_') -> handleSaveSectionTab.
Main session Ctrl+S still exports SF (same as before).

app/static/js/app.jsx

@@ -8065,7 +8065,13 @@ const App = () => {
       }
       if (ctrl && !alt && e.key === 's') {
         e.preventDefault();
-        handleExportSFS();
+        var curTab = activeTabRef.current;
+        if (curTab.startsWith('session_')) {
+          handleSaveSectionTab(curTab);
+          showToast('Đã lưu Section', 'success');
+        } else {
+          handleExportSFS();
+        }
         return;
       }
       if (ctrl && alt && e.key === 's' || ctrl && e.shiftKey && e.key === 's') {