Refactor expense form and add PDF generation functionality

- Update expense form fields (merchant->establishmentName, amount->price)
- Add PDF generation with Puppeteer integration
- Create PDFOptionsModal component for export options
- Update expense form validation and UI layout
- Add server API endpoint for PDF generation

pages/dashboard/expenses.vue

@@ -504,23 +504,26 @@ const generatePDF = async (options: any) => {
     });
     
     if (response.success && response.data) {
-      // For now, create HTML file instead of PDF since we're generating HTML content
-      const htmlContent = atob(response.data.content); // Decode base64
-      const blob = new Blob([htmlContent], { type: 'text/html' });
+      // Decode base64 PDF content
+      const pdfContent = atob(response.data.content);
+      
+      // Convert to byte array
+      const byteNumbers = new Array(pdfContent.length);
+      for (let i = 0; i < pdfContent.length; i++) {
+        byteNumbers[i] = pdfContent.charCodeAt(i);
+      }
+      const byteArray = new Uint8Array(byteNumbers);
+      
+      // Create PDF blob and download
+      const blob = new Blob([byteArray], { type: 'application/pdf' });
       const url = window.URL.createObjectURL(blob);
       const a = document.createElement('a');
       a.href = url;
-      a.download = `${options.documentName || 'expenses'}.html`;
+      a.download = response.data.filename;
       a.click();
       window.URL.revokeObjectURL(url);
       
-      // Also open in new tab for immediate viewing
-      const newTab = window.open();
-      if (newTab) {
-        newTab.document.open();
-        newTab.document.write(htmlContent);
-        newTab.document.close();
-      }
+      console.log('[expenses] PDF downloaded successfully:', response.data.filename);
     }
     
     showPDFModal.value = false;