refactor(docs): move integration doc to docs/ and add download link in settings

- Move ADMIN_PAYMENT_INTEGRATION_API.md → docs/ADMIN_PAYMENT_INTEGRATION_API.md
- Update README.md reference path
- Add payment integration doc download link in admin settings UI (Purchase section)
- Add i18n keys: integrationDoc / integrationDocHint (zh + en)

Author: touwaeriol

README.md

@@ -54,7 +54,7 @@ Sub2API is an AI API gateway platform designed to distribute and manage API quot
 ## Documentation
 
 - Dependency Security: `docs/dependency-security.md`
-- Admin Payment Integration API: `ADMIN_PAYMENT_INTEGRATION_API.md`
+- Admin Payment Integration API: `docs/ADMIN_PAYMENT_INTEGRATION_API.md`
 
 ---
 

ADMIN_PAYMENT_INTEGRATION_API.md docs/ADMIN_PAYMENT_INTEGRATION_API.mdADMIN_PAYMENT_INTEGRATION_API.md renamed to docs/ADMIN_PAYMENT_INTEGRATION_API.md

@@ -3590,7 +3590,9 @@ export default {
         urlPlaceholder: 'https://example.com/purchase',
         urlHint: 'Must be an absolute http(s) URL',
         iframeWarning:
-          '⚠️ iframe note: Some websites block embedding via X-Frame-Options or CSP (frame-ancestors). If the page is blank, provide an "Open in new tab" alternative.'
+          '⚠️ iframe note: Some websites block embedding via X-Frame-Options or CSP (frame-ancestors). If the page is blank, provide an "Open in new tab" alternative.',
+        integrationDoc: 'Payment Integration Docs',
+        integrationDocHint: 'Covers endpoint specs, idempotency semantics, and code samples'
       },
       soraClient: {
         title: 'Sora Client',

frontend/src/i18n/locales/en.ts

@@ -3762,7 +3762,9 @@ export default {
         urlPlaceholder: 'https://example.com/purchase',
         urlHint: '必须是完整的 http(s) 链接',
         iframeWarning:
-          '⚠️ iframe 提示：部分网站会通过 X-Frame-Options 或 CSP（frame-ancestors）禁止被 iframe 嵌入，出现空白时可引导用户使用”新窗口打开”。'
+          '⚠️ iframe 提示：部分网站会通过 X-Frame-Options 或 CSP（frame-ancestors）禁止被 iframe 嵌入，出现空白时可引导用户使用”新窗口打开”。',
+        integrationDoc: '支付集成文档',
+        integrationDocHint: '包含接口说明、幂等语义及示例代码'
       },
       soraClient: {
         title: 'Sora 客户端',

frontend/src/i18n/locales/zh.ts

@@ -991,6 +991,26 @@
                 {{ t('admin.settings.purchase.iframeWarning') }}
               </p>
             </div>
+
+            <!-- Integration Docs -->
+            <div class="flex items-center gap-2 text-sm">
+              <svg xmlns="http://www.w3.org/2000/svg" class="h-4 w-4 shrink-0 text-gray-400" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 12h6m-6 4h6m2 5H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z" />
+              </svg>
+              <a
+                href="https://raw.githubusercontent.com/Wei-Shaw/sub2api/main/docs/ADMIN_PAYMENT_INTEGRATION_API.md"
+                target="_blank"
+                rel="noopener noreferrer"
+                class="text-blue-600 hover:underline dark:text-blue-400"
+                download="ADMIN_PAYMENT_INTEGRATION_API.md"
+              >
+                {{ t('admin.settings.purchase.integrationDoc') }}
+              </a>
+              <span class="text-gray-400 dark:text-gray-500">—</span>
+              <span class="text-xs text-gray-500 dark:text-gray-400">
+                {{ t('admin.settings.purchase.integrationDocHint') }}
+              </span>
+            </div>
           </div>
         </div>