[Feature] 供应商Logo自定义及模型Logo适配

[zhy7201]

Affected area

Desktop UI (agent-gui / React)

Problem statement (what should this solve)

供应商Logo能自定义图标以及模型Logo适配，现在的Logo全都是一样的

Proposed behavior

能自定义供应商的Logo，模型Logo能自动适配。

Estimated change scope

No response

Alternatives considered

No response

Pre-submit checklist

• I searched existing issues and pull requests and found no duplicates.
• This proposal is focused on a single feature or improvement.
• I understand a PR should come after this issue is confirmed by maintainers, otherwise it will be converted to draft.