refactor: simplify translations — shared utils, deduplicated code

- Extract shared constants to client/src/utils/translations.js
  (AVAILABLE_LANGUAGES, TRANSLATION_STATUS_COLORS, isTextSelected, groupTextsByLanguage)
- TranslationDetailPanel: deduplicate copy button JSX, hoist hasSelected
- PublicTranslationReview: memoize textsByLanguage, use shared isTextSelected
- Translations page: import from shared module
- Server: translation schema updates, post_id linking
- Add reassign-user utility script
- Add new translation i18n keys to en.json and ar.json

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

client/src/utils/translations.js

@@ -0,0 +1,30 @@
+export const AVAILABLE_LANGUAGES = [
+  { code: 'AR', label: 'العربية' },
+  { code: 'EN', label: 'English' },
+  { code: 'FR', label: 'Français' },
+  { code: 'ID', label: 'Bahasa Indonesia' },
+]
+
+export const TRANSLATION_STATUS_COLORS = {
+  draft: 'bg-surface-tertiary text-text-secondary',
+  pending_review: 'bg-amber-100 text-amber-700',
+  approved: 'bg-emerald-100 text-emerald-700',
+  rejected: 'bg-red-100 text-red-700',
+  revision_requested: 'bg-orange-100 text-orange-700',
+}
+
+export function isTextSelected(text) {
+  return text.is_selected === true || text.is_selected === 1
+}
+
+export function groupTextsByLanguage(texts) {
+  const grouped = {}
+  for (const text of texts) {
+    if (!grouped[text.language_code]) grouped[text.language_code] = []
+    grouped[text.language_code].push(text)
+  }
+  for (const code in grouped) {
+    grouped[code].sort((a, b) => (a.option_number || 1) - (b.option_number || 1))
+  }
+  return grouped
+}