Add user filtering and progress overview to submissions page; enhance localization for user selection and progress display

stubs/api/data/stats-v2.json

@@ -200,6 +200,28 @@
     }
   ],
   "activeParticipants": [
+    {
+      "userId": "6909b51512c75d75a36a52bf",
+      "nickname": "Примаков А.А.",
+      "totalSubmissions": 14,
+      "completedTasks": 1,
+      "chainProgress": [
+          {
+              "chainId": "6909ad8612c75d75a36a4c58",
+              "chainName": "Это тестовая цепочка заданий",
+              "totalTasks": 2,
+              "completedTasks": 1,
+              "progressPercent": 50
+          },
+          {
+              "chainId": "690a30b1e723507972c44098",
+              "chainName": "Навыки работы с нейросетями для начинающих (пошагово)",
+              "totalTasks": 20,
+              "completedTasks": 1,
+              "progressPercent": 5
+          }
+      ]
+  },
     {
       "userId": "user_1",
       "nickname": "alex_dev",