feat: upgrade MiniMax default model to M2.7 (#737)

- Add MiniMax-M2.7 and MiniMax-M2.7-highspeed to model list
- Set MiniMax-M2.7 as default model
- Keep all previous models as alternatives
- Update docs in EN/CN/JA

Co-authored-by: PR Bot <pr-bot@minimaxi.com>

lib/types/model-config.ts

@@ -345,6 +345,8 @@ export const SUGGESTED_MODELS: Partial<Record<ProviderName, string[]>> = {
     ],
     minimax: [
         // MiniMax models (Anthropic-compatible API)
+        "MiniMax-M2.7",
+        "MiniMax-M2.7-highspeed",
         "MiniMax-M2.5",
         "MiniMax-M2.5-highspeed",
     ],