✨ feat(channel): Robust Vertex AI batch-key upload & stable multi-key settings

Summary
-------
1. Vertex AI JSON key upload
   • Accept multiple `.json` files (drag & drop / click).
   • Parse each `fileInstance`; build valid key array.
   • Malformed files are skipped and collected into **one** toast message.
   • Upload list now仅displays valid files; form state (`vertex_files`) 同步保持.
   • On *Submit* keys are re-parsed to prevent async timing loss.

2. Multi-key mode stability
   • Added `multi_key_mode: "random"` to initial form values.
   • `Form.Select` becomes fully controlled (`value`/`onChange`).
   • Toggling the “multi-key mode” checkbox writes default / removes field, so
     `setValues(inputs)` no longer clears the user’s choice.

3. UX / compatibility tweaks
   • Preserve uploaded files when editing any other field.
   • Use `fileInstance` only – compatible with legacy Semi Upload API.
   • Removed redundant `limit` prop on `Form.Upload`.
   • Aggregated error handling avoids toast spam.

Result
------
Channel creation/update now supports:
• Reliable batch import of Vertex AI service-account keys.
• Consistent retention of multi-key strategy (`random` / `polling`).
• Cleaner, user-friendly error feedback.

web/src/i18n/locales/en.json

@@ -1142,7 +1142,7 @@
   "鉴权json": "Authentication JSON",
   "请输入鉴权json": "Please enter authentication JSON",
   "组织": "Organization",
-  "组织，可选，不填则为默认组织": "Organization (optional), default if empty",
+  "组织，不填则为默认组织": "Organization, default if empty",
   "请输入组织org-xxx": "Please enter organization org-xxx",
   "默认测试模型": "Default Test Model",
   "不填则为模型列表第一个": "First model in list if empty",
@@ -1756,5 +1756,14 @@
   "生成数量必须大于0": "Generation quantity must be greater than 0",
   "创建后可在编辑渠道时获取上游模型列表": "After creation, you can get the upstream model list when editing the channel",
   "可用端点类型": "Supported endpoint types",
-  "未登录，使用默认分组倍率：": "Not logged in, using default group ratio: "
+  "未登录，使用默认分组倍率：": "Not logged in, using default group ratio: ",
+  "密钥聚合模式": "Key aggregation mode",
+  "随机": "Random",
+  "轮询": "Polling",
+  "密钥文件 (.json)": "Key file (.json)",
+  "点击上传文件或拖拽文件到这里": "Click to upload file or drag and drop file here",
+  "仅支持 JSON 文件，支持多文件": "Only JSON files are supported, multiple files are supported",
+  "请上传密钥文件": "Please upload the key file",
+  "请填写部署地区": "Please fill in the deployment region",
+  "请输入部署地区，例如：us-central1\n支持使用模型映射格式\n{\n    \"default\": \"us-central1\",\n    \"claude-3-5-sonnet-20240620\": \"europe-west1\"\n}": "Please enter the deployment region, for example: us-central1\nSupports using model mapping format\n{\n    \"default\": \"us-central1\",\n    \"claude-3-5-sonnet-20240620\": \"europe-west1\"\n}"
 }