fix(i18n): comprehensive translation audit and fixes across all 14 languages

- Fix critical bug: Photos and Files pages had German text hardcoded in JSX,
  now use t() keys visible correctly in all languages
- Add 16 new translation keys (photos/files UI, login validation, common errors,
  rate limit message) across all 14 language files
- Add missing keys in packing, memories, and budget sections for br, de, it, es,
  fr, nl, pl, cs, hu, ru, zh, zh-TW, ar
- Add 152+ missing keys for zh-TW (entire sections were absent)
- Change Vacay addon name to 'Férias' in pt-BR only
- Add client-side HTTP 429 interceptor that shows translated rate limit message
- Replace hardcoded English fallbacks in TripPlannerPage, DayPlanSidebar,
  DisplaySettingsTab, MapSettingsTab, AccountTab, and TodoListPanel with t()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/src/components/Settings/MapSettingsTab.tsx

@@ -74,7 +74,7 @@ export default function MapSettingsTab(): React.ReactElement {
       })
       toast.success(t('settings.toast.mapSaved'))
     } catch (err: unknown) {
-      toast.error(err instanceof Error ? err.message : 'Error')
+      toast.error(err instanceof Error ? err.message : t('common.error'))
     } finally {
       setSaving(false)
     }