feat(providers): add Minimax Coding (China) provider

- Add minimax-cn provider with China endpoint (api.minimaxi.com)
- Add provider icon and configuration
- Add validation and test support
- Add API configuration in open-sse

Co-authored-by: Blade096 <46746496+Blade096@users.noreply.github.com>
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/config/providerModels.js

@@ -189,6 +189,7 @@ export const PROVIDER_ID_TO_ALIAS = {
   glm: "glm",
   kimi: "kimi",
   minimax: "minimax",
+  "minimax-cn": "minimax",
 };
 
 export function getModelsByProviderId(providerId) {