🐛 fix: multi-key channel sync and Vertex-AI key-upload edge cases

Backend
1. controller/channel.go
   • Always hydrate `ChannelInfo` from DB in `UpdateChannel`, keeping `IsMultiKey` true so `MultiKeySize` is recalculated.

2. model/channel.go
   • getKeys(): accept both newline-separated keys and JSON array (`[ {...}, {...} ]`).
   • Update(): reuse new parser-logic to recalc `MultiKeySize`; prune stale indices in `MultiKeyStatusList`.

Frontend
1. pages/Channel/EditChannel.js
   • `handleVertexUploadChange`
     – Reset `vertexErroredNames` on every change so the “ignored files” prompt always re-appears.
     – In single-key mode keep only the last file; in batch mode keep all valid files.
     – Parse files, display “以下文件解析失败，已忽略：…”.
   • Batch-toggle checkbox
     – When switching from batch→single while multiple files are present, show a confirm dialog and retain only the first file (synchronises state, form and local caches).
   • On opening the “new channel” side-sheet, clear `vertexErroredNames` to restore error prompts.

Result
• “已启用 x/x” count updates immediately after editing multi-key channels.
• Vertex-AI key upload works intuitively: proper error feedback, no duplicated files, and safe down-switch from batch to single mode.

model/channel.go

@@ -71,7 +71,19 @@ func (channel *Channel) getKeys() []string {
 	if channel.Key == "" {
 		return []string{}
 	}
-	// use \n to split keys
+	trimmed := strings.TrimSpace(channel.Key)
+	// If the key starts with '[', try to parse it as a JSON array (e.g., for Vertex AI scenarios)
+	if strings.HasPrefix(trimmed, "[") {
+		var arr []json.RawMessage
+		if err := json.Unmarshal([]byte(trimmed), &arr); err == nil {
+			res := make([]string, len(arr))
+			for i, v := range arr {
+				res[i] = string(v)
+			}
+			return res
+		}
+	}
+	// Otherwise, fall back to splitting by newline
 	keys := strings.Split(strings.Trim(channel.Key, "\n"), "\n")
 	return keys
 }
@@ -396,23 +408,36 @@ func (channel *Channel) Insert() error {
 }
 
 func (channel *Channel) Update() error {
-	// 如果是多密钥渠道，则根据当前 key 列表重新计算 MultiKeySize，避免编辑密钥后数量未同步
+	// If this is a multi-key channel, recalculate MultiKeySize based on the current key list to avoid inconsistency after editing keys
 	if channel.ChannelInfo.IsMultiKey {
 		var keyStr string
 		if channel.Key != "" {
 			keyStr = channel.Key
 		} else {
-			// 如果当前未提供 key，读取数据库中的现有 key
+			// If key is not provided, read the existing key from the database
 			if existing, err := GetChannelById(channel.Id, true); err == nil {
 				keyStr = existing.Key
 			}
 		}
+		// Parse the key list (supports newline separation or JSON array)
 		keys := []string{}
 		if keyStr != "" {
-			keys = strings.Split(strings.Trim(keyStr, "\n"), "\n")
+			trimmed := strings.TrimSpace(keyStr)
+			if strings.HasPrefix(trimmed, "[") {
+				var arr []json.RawMessage
+				if err := json.Unmarshal([]byte(trimmed), &arr); err == nil {
+					keys = make([]string, len(arr))
+					for i, v := range arr {
+						keys[i] = string(v)
+					}
+				}
+			}
+			if len(keys) == 0 { // fallback to newline split
+				keys = strings.Split(strings.Trim(keyStr, "\n"), "\n")
+			}
 		}
 		channel.ChannelInfo.MultiKeySize = len(keys)
-		// 清理超过新 key 数量范围的状态数据，防止索引越界
+		// Clean up status data that exceeds the new key count to prevent index out of range
 		if channel.ChannelInfo.MultiKeyStatusList != nil {
 			for idx := range channel.ChannelInfo.MultiKeyStatusList {
 				if idx >= channel.ChannelInfo.MultiKeySize {