fix: hide past countdown heading

frontend/src/CountdownPanel.vue

@@ -84,7 +84,7 @@ const countdownGroups = computed<CountdownGroup[]>(() => {
   return [
     { key:'recent', title:'最近', items:recent },
     { key:'later', title:'稍后', items:later },
-    { key:'past', title:'已经过去', items:past },
+    { key:'past', title:'', items:past },
   ].filter((group) => group.items.length)
 })
 
@@ -189,7 +189,7 @@ onBeforeUnmount(() => { previousFocus = null })
         </button>
         <div v-if="countdownGroups.length" class="countdown-timeline">
           <section v-for="group in countdownGroups" :key="group.key" class="countdown-group">
-            <h3>{{group.title}}</h3>
+            <h3 v-if="group.title">{{group.title}}</h3>
             <button v-for="item in group.items" :key="item.id" type="button" class="countdown-row" :class="[`kind-${item.kind}`, { pinned:item.pinned, today:item.days===0, past:item.days<0 }]" @click="openDetail(item)">
               <span class="countdown-main"><b>{{item.title}}</b><small>{{primaryDate(item)}}<template v-if="secondaryDate(item)"> · {{secondaryDate(item)}}</template></small><span class="countdown-badges"><em v-for="badge in visibleBadges(item)" :key="badge">{{badge}}</em></span></span>
               <span class="countdown-state"><strong>{{item.days===0?'今天':Math.abs(item.days)}}</strong><small>{{countdownDayText(item.days)}}</small></span>