feat(settings): reorganize the settings dialog and the model settings

Tabs Models, General, Drawing and About, each with a fixed title row.

The models tab becomes three pages: the user's providers with one status
each and the server's models; a searchable picker of all 24 providers in
four groups; and a provider page in three steps (connection, models,
test). A new provider gets its first suggested model, and a passing test
offers to use the model in the chat. Bedrock asks for one way of signing
in, with an optional session token for temporary access keys.

The composer's model picker lists every model, marking untested and
failed ones, and can open the provider picker. A chat error that offers
model settings opens the provider the request went to.

docs/cn/admin-panel.md

@@ -9,7 +9,7 @@
 
 ## 可配置内容
 
-1. **Models（模型）** — 添加提供商及其 API Key 和模型列表，交互与应用内的模型设置相同。保存后这些模型成为所有用户可用的服务端模型，并在请求时与环境中的 `AI_MODELS_CONFIG` / `ai-models.json` 合并（面板不会修改这些环境文件）。
+1. **Models（模型）** — 添加提供商及其 API Key 和模型列表，凭据输入框与应用内的模型设置相同。保存后这些模型成为所有用户可用的服务端模型，并在请求时与环境中的 `AI_MODELS_CONFIG` / `ai-models.json` 合并（面板不会修改这些环境文件）。
 2. **其余区块** — 访问码、生成参数、功能开关、可观测性和配额。保存的设置会写入 `data/settings.json` 并立即生效，无需重启（少数设置如 Langfuse 和 DynamoDB 标记为"需要重启"）。
 
 ## 优先级