fix(i18n): add missing index page translation keys to en.json

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/translations/en.json

@@ -535,6 +535,7 @@
   "index.page_title_dashboard": "Dashboard",
   "index.page_title_public": "Intelligent Document Processing",
   "index.platform_overview": "Platform overview",
+  "index.processing_stats": "Processing Stats",
   "index.quick_actions": "Quick Actions",
   "index.quick_documents": "My Documents",
   "index.quick_documents_desc": "Browse your processed files",
@@ -553,9 +554,13 @@
   "index.stat_active_integrations": "Active Integrations",
   "index.stat_active_users": "Active users",
   "index.stat_files_month": "Files this month",
+  "index.stat_files_ocr": "Files with OCR",
   "index.stat_files_today": "Files today",
   "index.stat_storage_targets": "Storage Targets",
+  "index.stat_this_month": "This month",
+  "index.stat_today": "Today",
   "index.stat_total_files": "Total files",
+  "index.stat_total_processed": "Total processed",
   "index.tier_plan": "Plan",
   "index.tier_upgrade": "Upgrade",
   "index.tier_view_details": "View full details",