Fixed report rendering in web

lib/screens/reports/report_pdf_export.dart

@@ -1,4 +1,3 @@
-import 'dart:isolate';
 import 'dart:typed_data';
 import 'dart:ui' as ui;
 
@@ -72,8 +71,7 @@ class ReportPdfExport {
     final generated = AppTime.formatDate(AppTime.now());
     final dateLabel = dateRange.label;
 
-    // ── Build the PDF on a background isolate so it doesn't freeze the UI ──
+    // ── Build the PDF on the main thread (dart:isolate is not supported on web) ──
-    return Isolate.run(() {
     return _buildPdfBytes(
       chartImages: chartImages,
       dateRangeText: dateRangeText,
@@ -83,11 +81,9 @@ class ReportPdfExport {
       boldFontData: boldFontData.buffer.asUint8List(),
       logoBytes: logoBytes,
     );
-    });
   }
 
   /// Pure function that assembles the PDF document from raw data.
-  /// Designed to run inside [Isolate.run].
   static Future<Uint8List> _buildPdfBytes({
     required Map<String, Uint8List> chartImages,
     required String dateRangeText,