Phase 6: Translate User Pages - exchange, trades, invites, profile

- Expand exchange.json with all exchange page strings (page, steps, detailsStep, bookingStep, confirmationStep, priceDisplay)
- Create trades.json translation files for es, en, ca
- Create invites.json translation files for es, en, ca
- Create profile.json translation files for es, en, ca
- Translate exchange page and all components (ExchangeDetailsStep, BookingStep, ConfirmationStep, StepIndicator, PriceDisplay)
- Translate trades page (titles, sections, buttons, status labels)
- Translate invites page (titles, sections, status badges, copy button)
- Translate profile page (form labels, hints, placeholders, messages)
- Update IntlProvider to load all new namespaces
- All frontend tests passing

frontend/app/exchange/page.tsx

@@ -19,6 +19,7 @@ import { StepIndicator } from "./components/StepIndicator";
 import { ExchangeDetailsStep } from "./components/ExchangeDetailsStep";
 import { BookingStep } from "./components/BookingStep";
 import { ConfirmationStep } from "./components/ConfirmationStep";
+import { useTranslation } from "../hooks/useTranslation";
 
 type ExchangeResponse = components["schemas"]["ExchangeResponse"];
 
@@ -57,6 +58,7 @@ const styles = {
 
 export default function ExchangePage() {
   const router = useRouter();
+  const t = useTranslation("exchange");
   const { user, isLoading, isAuthorized } = useRequireAuth({
     requiredPermission: Permission.CREATE_EXCHANGE,
     fallbackRedirect: "/",
@@ -281,8 +283,8 @@ export default function ExchangePage() {
     <main style={layoutStyles.main}>
       <Header currentPage="exchange" />
       <div style={styles.content}>
-        <h1 style={typographyStyles.pageTitle}>Exchange Bitcoin</h1>
-        <p style={typographyStyles.pageSubtitle}>Buy or sell Bitcoin with a 5% premium</p>
+        <h1 style={typographyStyles.pageTitle}>{t("page.title")}</h1>
+        <p style={typographyStyles.pageSubtitle}>{t("page.subtitle")}</p>
 
         {error && (
           <div style={bannerStyles.errorBanner}>
@@ -290,7 +292,7 @@ export default function ExchangePage() {
             {existingTradeId && (
               <div style={styles.errorLink}>
                 <a href={`/trades/${existingTradeId}`} style={styles.errorLinkAnchor}>
-                  View your existing trade →
+                  {t("page.viewExistingTrade")}
                 </a>
               </div>
             )}