fix: 移除不存在的 Crown 图标

frontend/src/components/LevelUpDialog.vue

@@ -64,7 +64,7 @@ import { ref, computed, watch } from 'vue'
 import { 
   TrendCharts, Medal, Star, Reading, Collection, Files, 
   Select, Finished, Trophy, Clock, Timer, Stopwatch, 
-  Operation, Calendar, Rank, Crown, Headset, StarFilled 
+  Operation, Calendar, Rank, Headset, StarFilled 
 } from '@element-plus/icons-vue'
 
 interface Badge {
@@ -107,7 +107,7 @@ const visible = computed({
 const iconMap: Record<string, any> = {
   Medal, Star, Reading, Collection, Files, Select,
   Finished, Trophy, TrendCharts, Clock, Timer,
-  Stopwatch, Operation, Calendar, Rank, Crown,
+  Stopwatch, Operation, Calendar, Rank,
   Headset, StarFilled
 }