fix: load translations from API instead of static CDN files

The banner was fetching /translations-{locale}.json from the CDN as
static files, but translations are stored in the DB and served via
the public /api/v1/translations/{siteId}/{locale} endpoint.

Fixes:
- fetchTranslations() now calls the public API endpoint
- loadTranslations() takes (apiBase, siteId, locale)
- banner.ts passes apiBase and siteId to loadTranslations()
- i18n.test.ts updated to match new signature

apps/banner/src/i18n.ts

@@ -84,34 +84,38 @@ export function normaliseLocale(locale: string): string {
 }
 
 /**
- * Fetch translations for a locale from the CDN.
+ * Fetch translations for a locale from the public API endpoint.
  * Returns null if not found or on error.
  */
 export async function fetchTranslations(
-  cdnBase: string,
+  apiBase: string,
+  siteId: string,
   locale: string,
 ): Promise<Partial<TranslationStrings> | null> {
   try {
-    const resp = await fetch(`${cdnBase}/translations-${locale}.json`);
+    const resp = await fetch(`${apiBase}/api/v1/translations/${siteId}/${locale}`);
     if (!resp.ok) return null;
-    return (await resp.json()) as Partial<TranslationStrings>;
+    // API returns { strings: { ... } }
+    const data = (await resp.json()) as { strings?: Partial<TranslationStrings> };
+    return data.strings ?? null;
   } catch {
     return null;
   }
 }
 
 /**
- * Load translations: try fetching from CDN, fall back to defaults.
+ * Load translations: try fetching from API, fall back to defaults.
  */
 export async function loadTranslations(
-  cdnBase: string,
+  apiBase: string,
+  siteId: string,
   locale: string,
 ): Promise<TranslationStrings> {
   if (locale === 'en') {
     return { ...DEFAULT_TRANSLATIONS };
   }
 
-  const remote = await fetchTranslations(cdnBase, locale);
+  const remote = await fetchTranslations(apiBase, siteId, locale);
   if (!remote) {
     return { ...DEFAULT_TRANSLATIONS };
   }