QR upload: replace inline hint with dialog, add back button in brand page

- Replace the inline brand-upload-hint bar in RecipeDetailOverlay with a
  confirm dialog (「去上传」/「取消」) that pops up when the card opens
- Extend useDialog/CustomDialog to support custom ok/cancel button text
- Add a 「← 返回配方卡片」banner in MyDiary brand tab when navigated
  from a recipe card, allowing return without uploading

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/views/MyDiary.vue

@@ -107,6 +107,11 @@
 
     <!-- Brand Tab -->
     <div v-if="activeTab === 'brand'" class="tab-content">
+      <!-- Back to recipe card (when navigated from a recipe) -->
+      <div v-if="returnRecipeId" class="return-banner">
+        <span>📋 上传完成后可返回配方卡片</span>
+        <button class="btn-return" @click="goBackToRecipe">← 返回配方卡片</button>
+      </div>
       <div class="section-card">
         <h4>🏷️ 品牌设置</h4>
 
@@ -232,6 +237,7 @@ const router = useRouter()
 const activeTab = ref('brand')
 const pasteText = ref('')
 const selectedDiaryId = ref(null)
+const returnRecipeId = ref(null)
 const selectedDiary = ref(null)
 const newEntryText = ref('')
 
@@ -266,8 +272,16 @@ onMounted(async () => {
   await diaryStore.loadDiary()
   displayName.value = auth.user.display_name || ''
   await loadBrandSettings()
+  returnRecipeId.value = localStorage.getItem('oil_return_recipe_id') || null
 })
 
+function goBackToRecipe() {
+  if (returnRecipeId.value) {
+    localStorage.removeItem('oil_return_recipe_id')
+    router.push('/?openRecipe=' + encodeURIComponent(returnRecipeId.value))
+  }
+}
+
 function selectDiary(d) {
   const id = d._id || d.id
   selectedDiaryId.value = id
@@ -755,6 +769,39 @@ async function applyBusiness() {
   border-color: #7ec6a4;
 }
 
+/* Return banner */
+.return-banner {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  background: #f0faf5;
+  border: 1.5px solid #7ec6a4;
+  border-radius: 12px;
+  padding: 10px 14px;
+  margin-bottom: 14px;
+  font-size: 13px;
+  color: #3e7d5a;
+  gap: 10px;
+}
+
+.btn-return {
+  background: linear-gradient(135deg, #7ec6a4 0%, #4a9d7e 100%);
+  color: #fff;
+  border: none;
+  border-radius: 8px;
+  padding: 6px 14px;
+  font-size: 12px;
+  cursor: pointer;
+  font-family: inherit;
+  font-weight: 500;
+  white-space: nowrap;
+  flex-shrink: 0;
+}
+
+.btn-return:hover {
+  opacity: 0.9;
+}
+
 /* Brand */
 .form-group {
   margin-bottom: 14px;