feat(currency): sweep remaining concat call sites to formatCurrency

Builds on the centralised formatter shipped in ee2da8f. Replaces
\`\${currency} \${amount}\` style concatenations across the dashboard
revenue tooltip, command-search invoice/expense fallback labels,
expense-duplicate banner, and the invoice + expense PDF templates.
Drops the duplicate \`currencySymbol\` helper inside expense-pdf.service
in favour of the shared util; the two PDF helpers (renderReceiptHeader,
addReceiptErrorPage) now take a currency code instead of a pre-rendered
symbol so the formatter is the single source for spacing + thousands
separators. Also re-runs Prettier on the files where the prior commit
shipped without it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(portal)/portal/invoices/page.tsx

@@ -27,9 +27,7 @@ export default async function PortalInvoicesPage() {
     <div className="space-y-6">
       <div>
         <h1 className="text-2xl font-semibold text-gray-900">Invoices</h1>
-        <p className="text-sm text-gray-500 mt-1">
-          Your billing statements and payment history
-        </p>
+        <p className="text-sm text-gray-500 mt-1">Your billing statements and payment history</p>
       </div>
 
       {invoices.length === 0 ? (
@@ -43,10 +41,7 @@ export default async function PortalInvoicesPage() {
       ) : (
         <div className="space-y-3">
           {invoices.map((invoice) => (
-            <div
-              key={invoice.id}
-              className="bg-white rounded-lg border p-5"
-            >
+            <div key={invoice.id} className="bg-white rounded-lg border p-5">
               <div className="flex items-start justify-between gap-4 flex-wrap">
                 <div className="flex-1 min-w-0">
                   <div className="flex items-center gap-3">