feat: dual-path save for format=jpg/jpeg with ?save=true

When format=jpg/jpeg and save=true, the chart is now saved to both:
- SavePath/{isin}.jpg  (visible filename)
- SavePathEnc/{alias}.jpg  (encoded filename, if alias exists)

This allows the external script to call the API once instead of twice
(no more separate jpg + jpgEnc calls). format=jpgEnc remains unchanged
for backward compatibility.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

CertReports.Syncfusion/Controllers/ChartController.cs

@@ -121,15 +121,28 @@ public class ChartController : ControllerBase
                           || format.Equals("jpg",  StringComparison.OrdinalIgnoreCase)
                           || format.Equals("jpeg", StringComparison.OrdinalIgnoreCase);
 
-            // Alias codificato (necessario sia per jpgEnc che per il salvataggio su disco)
-            string? alias = isJpegEnc ? await _chartDataServiceV2.GetChartAliasAsync(isin) : null;
+            // Alias: serve per jpgEnc (nome file risposta) e per il doppio salvataggio in jpg/jpeg
+            string? alias = (isJpegEnc || (isJpeg && save))
+                ? await _chartDataServiceV2.GetChartAliasAsync(isin)
+                : null;
 
             byte[] imgBytes = SkiaChartRendererV2.RenderToPng(chartData, width, height, jpeg: isJpeg);
 
             // ── Salvataggio su disco (solo se ?save=true) ─────────────────
             if (save && isJpeg)
             {
-                await SaveChartToDiskAsync(isin, alias, imgBytes, isJpegEnc);
+                if (isJpegEnc)
+                {
+                    // jpgEnc: solo SavePathEnc/{alias}.jpg
+                    await SaveChartToDiskAsync(isin, alias, imgBytes, isEnc: true);
+                }
+                else
+                {
+                    // jpg/jpeg: SavePath/{isin}.jpg + SavePathEnc/{alias}.jpg
+                    await SaveChartToDiskAsync(isin, alias: null, imgBytes, isEnc: false);
+                    if (!string.IsNullOrEmpty(alias))
+                        await SaveChartToDiskAsync(isin, alias, imgBytes, isEnc: true);
+                }
             }
 
             if (format.Equals("pdf", StringComparison.OrdinalIgnoreCase))