🐛 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.

web/src/components/table/ChannelsTable.js

@@ -987,7 +987,6 @@ const ChannelsTable = () => {
   };
 
   useEffect(() => {
-    // console.log('default effect')
     const localIdSort = localStorage.getItem('id-sort') === 'true';
     const localPageSize =
       parseInt(localStorage.getItem('page-size')) || ITEMS_PER_PAGE;