feat(presets): add OpenCode Go referral link and promo copy without partner badge

Decouple the in-app promotion banner from isPartner so a preset can show a
promo phrase plus referral link without earning the paid-partner star.

- ApiKeySection: gate the banner on partnerPromotionKey alone; the star is
  still driven solely by isPartner. This also un-suppresses the existing
  MiniMax cn/en promos, which already carried copy without isPartner.
- OpenCode Go (claude/codex/opencode): point apiKeyUrl at the referral
  link and add partnerPromotionKey "opencode_go" (no isPartner set).
- i18n: add the opencode_go promo string across zh/en/ja/zh-TW.

src/components/providers/forms/shared/ApiKeySection.tsx

@@ -29,7 +29,6 @@ export function ApiKeySection({
   websiteUrl,
   placeholder,
   disabled,
-  isPartner,
   partnerPromotionKey,
 }: ApiKeySectionProps) {
   const { t } = useTranslation();
@@ -73,8 +72,8 @@ export function ApiKeySection({
             })}
           </a>
 
-          {/* 合作伙伴促销信息 */}
-          {isPartner && partnerPromotionKey && (
+          {/* 促销信息（与 isPartner 解耦：仅凭 partnerPromotionKey 即可展示，星标仍由 isPartner 控制） */}
+          {partnerPromotionKey && (
             <div className="rounded-md bg-blue-50 dark:bg-blue-950/30 p-2.5 border border-blue-200 dark:border-blue-800">
               <p className="text-xs leading-relaxed text-blue-700 dark:text-blue-300">
                 💡{" "}