feat(i18n): add Czech locale translations

Add Czech (cs) translations for contact-facing pages and email footers,
and wire up the locale in the i18n system with the correct flag.

packages/shared/src/i18n/index.ts

@@ -7,6 +7,7 @@ import deTranslations from './locales/de.json' with {type: 'json'};
 import hiTranslations from './locales/hi.json' with {type: 'json'};
 import ptTranslations from './locales/pt.json' with {type: 'json'};
 import bgTranslations from './locales/bg.json' with {type: 'json'};
+import csTranslations from './locales/cs.json' with {type: 'json'};
 export {
   SUPPORTED_LANGUAGES,
   DEFAULT_LANGUAGE,
@@ -38,6 +39,7 @@ const translationsMap: Record<string, Translations> = {
   hi: hiTranslations,
   pt: ptTranslations,
   bg: bgTranslations,
+  cs: csTranslations,
 };
 
 // In-memory cache for loaded translations