fix: AdminView 保存配置前先加载现有数据

- 避免空对象覆盖数据库中的现有配置
- 保存前先 GET 当前配置
- 合并修改的字段后再 POST
- 确保所有字段都正确保存

src/views/AdminView.vue

@@ -1141,26 +1141,30 @@ async function saveConfig() {
   configSaving.value = true
   configSaveMsg.value = ''
   try {
+    const res = await fetch('/api/v1/admin/config')
+    if (!res.ok) throw new Error(`Failed to load current config: HTTP ${res.status}`)
+    const currentConfig = await res.json()
+    
     const payload = {
       version: '1.0.0',
-      vlm_prompts: vlmPrompts.value,
-      llm_config: llmConfig.value,
-      processor_config: processorConfig.value,
-      filter_config: filterConfig.value,
-      system_config: systemConfig.value,
+      vlm_prompts: Object.keys(vlmPrompts.value).length > 0 ? vlmPrompts.value : currentConfig.vlm_prompts || {},
+      llm_config: Object.keys(llmConfig.value).length > 0 ? llmConfig.value : currentConfig.llm_config || {},
+      processor_config: Object.keys(processorConfig.value).length > 0 ? processorConfig.value : currentConfig.processor_config || {},
+      filter_config: Object.keys(filterConfig.value).length > 0 ? filterConfig.value : currentConfig.filter_config || {},
+      system_config: Object.keys(systemConfig.value).length > 0 ? systemConfig.value : currentConfig.system_config || {},
       search: {
         vlm_min_score: searchConfig.value.vlm_min_score || 0.0,
         vlm_max_results: searchConfig.value.vlm_max_results || 5,
         vlm_output_language: searchConfig.value.vlm_output_language || 'en'
       },
     }
-    const res = await fetch('/api/v1/admin/config', {
+    const saveRes = await fetch('/api/v1/admin/config', {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify(payload),
     })
-    if (!res.ok) throw new Error(`HTTP ${res.status}`)
-    const data = await res.json()
+    if (!saveRes.ok) throw new Error(`HTTP ${saveRes.status}`)
+    const data = await saveRes.json()
     configSaveOk.value = true
     configSaveMsg.value = 'Config saved successfully'
   } catch (e: any) {