fix: 选择容量时自动显示椰子油行 + 收回标签清除筛选

- 选容量后椰子油行自动出现（单次默认10滴，其他默认填满）
- 收回标签栏时清除所有标签筛选

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/views/RecipeManager.vue

@@ -42,7 +42,7 @@
       <button class="action-chip" :class="{ active: isAllSelected }" @click="toggleSelectAll">
         全选<span v-if="totalSelected > 0" class="chip-count">{{ totalSelected }}</span>
       </button>
-      <button class="action-chip" :class="{ active: showTagFilter }" @click="showTagFilter = !showTagFilter">标签</button>
+      <button class="action-chip" :class="{ active: showTagFilter }" @click="toggleTagFilter">标签</button>
       <button v-if="totalSelected > 0" class="action-chip" :class="{ active: showBatchMenu }" @click="showBatchMenu = !showBatchMenu">批量</button>
       <button v-if="totalSelected > 0" class="action-chip cancel" @click="clearSelection">取消</button>
       <button v-if="auth.isAdmin" class="export-btn" @click="exportExcel" title="导出Excel">📥</button>
@@ -443,7 +443,13 @@ const formCustomVolume = ref(null)
 const formCustomUnit = ref('drops')
 const formDilution = ref(6)
 
-const formCocoRow = ref({ oil: '椰子油', drops: 10, _search: '椰子油', _open: false })
+const formCocoRow = ref(null)
+
+watch(() => formVolume.value, (vol) => {
+  if (vol && !formCocoRow.value) {
+    formCocoRow.value = { oil: '椰子油', drops: vol === 'single' ? 10 : 0, _search: '椰子油', _open: false }
+  }
+})
 
 // EO ingredients (everything except coconut)
 const formEoIngredients = computed(() =>
@@ -562,6 +568,15 @@ async function deleteGlobalTag(tag) {
   }
 }
 
+function toggleTagFilter() {
+  if (showTagFilter.value) {
+    showTagFilter.value = false
+    selectedTags.value = []
+  } else {
+    showTagFilter.value = true
+  }
+}
+
 function toggleTag(tag) {
   const idx = selectedTags.value.indexOf(tag)
   if (idx >= 0) selectedTags.value.splice(idx, 1)