fix(i18n): standardize ellipsis to three dots (...) for consistency

Revert common.loading and common.saving from Unicode ellipsis (…) back to
three dots (...) to match the rest of the project (e.g. "Optional caption...").
Update 4 test files that were incorrectly using the Unicode ellipsis character.

client/src/i18n/translations/en.ts

@@ -5,7 +5,7 @@ const en: Record<string, string | { name: string; category: string }[]> = {
   'common.delete': 'Delete',
   'common.edit': 'Edit',
   'common.add': 'Add',
-  'common.loading': 'Loading…',
+  'common.loading': 'Loading...',
   'common.import': 'Import',
   'common.error': 'Error',
   'common.unknownError': 'Unknown error',
@@ -27,7 +27,7 @@ const en: Record<string, string | { name: string; category: string }[]> = {
   'common.name': 'Name',
   'common.email': 'Email',
   'common.password': 'Password',
-  'common.saving': 'Saving…',
+  'common.saving': 'Saving...',
   'common.justNow': 'just now',
   'common.hoursAgo': '{count}h ago',
   'common.daysAgo': '{count}d ago',