feat: 狩猎任务图标按难度区分颜色

- 炼狱难度：红色调
- 困难难度：橙色调
- 普通难度：原色

Build_God_Game/src/views/DailyMissionView.vue

@@ -145,13 +145,28 @@ const getProgressText = (mission: DailyMission) => {
   return `${targetType} ${progress.currentCount}/${progress.targetCount} ${targetName}`
 }
 
-const getMissionIcon = (type: MissionType) => {
+const getMissionIcon = (type: MissionType, difficulty: MissionDifficulty) => {
   if (type === MissionType.Collection) {
     return collectionIcon
   }
+  // For hunting, use different filters based on difficulty
   return huntingNormalIcon
 }
 
+const getMissionIconFilter = (type: MissionType, difficulty: MissionDifficulty) => {
+  if (type === MissionType.Collection) {
+    return 'none'
+  }
+  switch (difficulty) {
+    case MissionDifficulty.Purgatory:
+      return 'hue-rotate(-10deg) saturate(1.5) brightness(0.8)'
+    case MissionDifficulty.Hard:
+      return 'hue-rotate(-30deg) saturate(1.2)'
+    default:
+      return 'none'
+  }
+}
+
 const MissionCardContent = defineComponent({
   name: 'MissionCardContent',
   props: {
@@ -165,7 +180,7 @@ const MissionCardContent = defineComponent({
     return () => h('div', { class: 'mission-card-content' }, [
       h('div', { class: 'card-header' }, [
         h('div', { class: 'card-title-row' }, [
-          h('div', { class: 'card-icon', innerHTML: getMissionIcon(props.mission.missionType) }),
+          h('div', { class: 'card-icon', style: `filter: ${getMissionIconFilter(props.mission.missionType, props.mission.difficulty)}`, innerHTML: getMissionIcon(props.mission.missionType, props.mission.difficulty) }),
           h('span', { class: 'card-title' }, props.mission.missionTitle),
         ]),
         h('span', { class: ['card-status', getStatusClass(props.mission.status)] }, getStatusText(props.mission.status)),