feat: 配方卡片加入上传个人二维码功能

- RecipeDetailOverlay: 未上传二维码/背景图时，卡片上方显示提示横幅，下方出现「上传我的二维码」按钮，点击跳转到 MyDiary 品牌设置页并记录来源配方
- MyDiary: 新增二维码图片上传区域（直接上传图片文件，存为 base64 → PUT /api/brand qr_code 字段）；上传成功后若有待返回配方则自动跳回配方卡片；修复 loadBrandSettings 字段名与后端不一致的问题
- RecipeSearch: 支持 ?openRecipe= 查询参数，页面挂载时自动打开指定配方卡片，实现从 MyDiary 上传后无缝返回

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

frontend/src/views/MyDiary.vue

@@ -123,6 +123,16 @@
           </div>
         </div>
 
+        <div class="form-group">
+          <label>我的二维码图片</label>
+          <div class="upload-area" @click="triggerUpload('qr')">
+            <img v-if="brandQrImage" :src="brandQrImage" class="upload-preview qr-upload-preview" />
+            <span v-else class="upload-hint">📲 点击上传二维码图片</span>
+          </div>
+          <input ref="qrInput" type="file" accept="image/*" style="display:none" @change="handleUpload('qr', $event)" />
+          <div class="field-hint">上传后将显示在配方卡片右下角</div>
+        </div>
+
         <div class="form-group">
           <label>品牌Logo</label>
           <div class="upload-area" @click="triggerUpload('logo')">
@@ -202,6 +212,7 @@
 
 <script setup>
 import { ref, computed, onMounted, watch } from 'vue'
+import { useRouter } from 'vue-router'
 import { useAuthStore } from '../stores/auth'
 import { useOilsStore } from '../stores/oils'
 import { useDiaryStore } from '../stores/diary'
@@ -214,6 +225,7 @@ const auth = useAuthStore()
 const oils = useOilsStore()
 const diaryStore = useDiaryStore()
 const ui = useUiStore()
+const router = useRouter()
 
 const activeTab = ref('brand')
 const pasteText = ref('')
@@ -224,10 +236,12 @@ const newEntryText = ref('')
 // Brand settings
 const brandName = ref('')
 const brandQrUrl = ref('')
+const brandQrImage = ref('')
 const brandLogo = ref('')
 const brandBg = ref('')
 const logoInput = ref(null)
 const bgInput = ref(null)
+const qrInput = ref(null)
 
 // Account settings
 const displayName = ref('')
@@ -345,8 +359,9 @@ async function loadBrandSettings() {
       const data = await res.json()
       brandName.value = data.brand_name || ''
       brandQrUrl.value = data.qr_url || ''
-      brandLogo.value = data.logo_url || ''
-      brandBg.value = data.bg_url || ''
+      brandQrImage.value = data.qr_code || ''
+      brandLogo.value = data.brand_logo || ''
+      brandBg.value = data.brand_bg || ''
     }
   } catch {
     // no brand settings yet
@@ -369,26 +384,46 @@ async function saveBrandSettings() {
 
 function triggerUpload(type) {
   if (type === 'logo') logoInput.value?.click()
-  else bgInput.value?.click()
+  else if (type === 'bg') bgInput.value?.click()
+  else if (type === 'qr') qrInput.value?.click()
+}
+
+function readFileAsBase64(file) {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader()
+    reader.onload = e => resolve(e.target.result)
+    reader.onerror = reject
+    reader.readAsDataURL(file)
+  })
 }
 
 async function handleUpload(type, event) {
   const file = event.target.files[0]
   if (!file) return
-  const formData = new FormData()
-  formData.append('file', file)
-  formData.append('type', type)
   try {
-    const token = localStorage.getItem('oil_auth_token') || ''
-    const res = await fetch('/api/brand-upload', {
-      method: 'POST',
-      headers: token ? { Authorization: 'Bearer ' + token } : {},
-      body: formData,
+    const base64 = await readFileAsBase64(file)
+    const fieldMap = { logo: 'brand_logo', bg: 'brand_bg', qr: 'qr_code' }
+    const field = fieldMap[type]
+    if (!field) return
+    const res = await api('/api/brand', {
+      method: 'PUT',
+      body: JSON.stringify({ [field]: base64 }),
     })
     if (res.ok) {
-      const data = await res.json()
-      if (type === 'logo') brandLogo.value = data.url
-      else brandBg.value = data.url
+      if (type === 'logo') brandLogo.value = base64
+      else if (type === 'bg') brandBg.value = base64
+      else if (type === 'qr') {
+        brandQrImage.value = base64
+        // If user came here from a recipe card, navigate back
+        const returnRecipeId = localStorage.getItem('oil_return_recipe_id')
+        if (returnRecipeId) {
+          localStorage.removeItem('oil_return_recipe_id')
+          ui.showToast('二维码已上传，返回配方卡片 ✨')
+          await new Promise(r => setTimeout(r, 800))
+          router.push('/?openRecipe=' + encodeURIComponent(returnRecipeId))
+          return
+        }
+      }
       ui.showToast('上传成功')
     }
   } catch {
@@ -783,6 +818,18 @@ async function applyBusiness() {
   max-height: 100px;
 }
 
+.qr-upload-preview {
+  max-width: 120px;
+  max-height: 120px;
+}
+
+.field-hint {
+  font-size: 12px;
+  color: #9b94a3;
+  margin-top: 4px;
+  padding-left: 2px;
+}
+
 .upload-hint {
   font-size: 13px;
   color: #b0aab5;