Add user stats page and refactor user navigation; replace modal with dedicated page for user statistics, enhancing routing and UI consistency. Update localization for new status keys in both English and Russian.

locales/en.json

@@ -137,9 +137,12 @@
   "challenge.admin.users.stats.chains.progress": "Chain progress",
   "challenge.admin.users.stats.tasks": "Tasks",
   "challenge.admin.users.stats.status.completed": "Completed",
+  "challenge.admin.users.stats.status.accepted": "Accepted",
   "challenge.admin.users.stats.status.needs_revision": "Revision",
   "challenge.admin.users.stats.status.in_progress": "In progress",
+  "challenge.admin.users.stats.status.pending": "Pending",
   "challenge.admin.users.stats.status.not_started": "Not started",
+  "challenge.admin.users.stats.status.not_attempted": "Not attempted",
   "challenge.admin.users.stats.attempts": "Attempts:",
   "challenge.admin.users.stats.avg.check.time": "Average check time",
   "challenge.admin.users.stats.close": "Close",