feat: add i18n dictionaries and service data

Locale-aware EN/FR string dictionaries and the two-service data model
(CVE Watch with per-locale URLs, Convert with a single URL).

src/i18n/locale.ts

@@ -0,0 +1,11 @@
+export type Locale = 'en' | 'fr';
+
+export const locales: Locale[] = ['en', 'fr'];
+
+export function otherLocale(locale: Locale): Locale {
+  return locale === 'en' ? 'fr' : 'en';
+}
+
+export function swapLocalePath(pathname: string, from: Locale, to: Locale): string {
+  return pathname.replace(`/${from}/`, `/${to}/`);
+}