Translate admin pages - Create admin.json files and translate all admin pages

- Create admin.json translation files for es, en, ca with all admin strings
- Update IntlProvider to include admin namespace
- Translate admin/invites/page.tsx - all strings now use translations
- Translate admin/trades/page.tsx - all strings now use translations
- Translate admin/price-history/page.tsx - all strings now use translations
- Translate admin/availability/page.tsx - all strings now use translations
- Add 'saving' key to common.json for all languages
- Fix linting errors: add t to useCallback dependencies
- All admin pages now fully multilingual

frontend/app/components/IntlProvider.tsx

@@ -26,6 +26,9 @@ import caInvites from "../../locales/ca/invites.json";
 import esProfile from "../../locales/es/profile.json";
 import enProfile from "../../locales/en/profile.json";
 import caProfile from "../../locales/ca/profile.json";
+import esAdmin from "../../locales/es/admin.json";
+import enAdmin from "../../locales/en/admin.json";
+import caAdmin from "../../locales/ca/admin.json";
 
 const messages = {
   es: {
@@ -36,6 +39,7 @@ const messages = {
     trades: esTrades,
     invites: esInvites,
     profile: esProfile,
+    admin: esAdmin,
   },
   en: {
     common: enCommon,
@@ -45,6 +49,7 @@ const messages = {
     trades: enTrades,
     invites: enInvites,
     profile: enProfile,
+    admin: enAdmin,
   },
   ca: {
     common: caCommon,
@@ -54,6 +59,7 @@ const messages = {
     trades: caTrades,
     invites: caInvites,
     profile: caProfile,
+    admin: caAdmin,
   },
 };