refactor(preset): remove AiHubMix hardcoded API_KEY in favor of generic auth selector

AiHubMix was the only preset that hardcoded ANTHROPIC_API_KEY before the
generic auth field selector was introduced. Now that users can freely
choose between AUTH_TOKEN and API_KEY via the UI, remove the special-case
and default AiHubMix to the standard ANTHROPIC_AUTH_TOKEN.

src/config/claudeProviderPresets.ts

@@ -316,12 +316,10 @@ export const providerPresets: ProviderPreset[] = [
     name: "AiHubMix",
     websiteUrl: "https://aihubmix.com",
     apiKeyUrl: "https://aihubmix.com",
-    // 说明：该供应商使用 ANTHROPIC_API_KEY（而非 ANTHROPIC_AUTH_TOKEN）
-    apiKeyField: "ANTHROPIC_API_KEY",
     settingsConfig: {
       env: {
         ANTHROPIC_BASE_URL: "https://aihubmix.com",
-        ANTHROPIC_API_KEY: "",
+        ANTHROPIC_AUTH_TOKEN: "",
       },
     },
     // 请求地址候选（用于地址管理/测速），用户可自行选择/覆盖