refactor: remove InvoiceView component and update related email and invoice handling

- Deleted the InvoiceView component to streamline the codebase.
- Updated EmailPreview and SendEmailDialog components to include currency and notes fields.
- Enhanced invoice-form to handle default hourly rates and improved item mapping.
- Refactored email template generation to include notes and currency formatting.
- Adjusted API routers for invoices to calculate totals and handle notes and currency correctly.

src/app/dashboard/invoices/[id]/page.tsx

@@ -99,10 +99,10 @@ function InvoiceViewContent({ invoiceId }: { invoiceId: string }) {
     }).format(new Date(date));
   };
 
-  const formatCurrency = (amount: number) => {
+  const formatCurrency = (amount: number, currency = invoice.currency) => {
     return new Intl.NumberFormat("en-US", {
       style: "currency",
-      currency: "USD",
+      currency,
     }).format(amount);
   };