fix(nginx): 将原生模型接口转发至 API

生产同构 Gemini 验收发现 /v1beta 请求被 Web 入口返回 405，导致请求在到达 Worker 前全部失败。补齐 /v1 和 /v1beta 原生兼容路由，沿用 API 的长请求超时、无缓冲和双上游故障切换配置。\n\n验证：使用 nginx:1.27-alpine 对完整站点配置执行 nginx -t 通过。

deploy/nginx/ai.51easyai.com-cluster.conf

@@ -56,6 +56,26 @@ server {
     proxy_pass http://easyai_gateway_api;
   }
 
+  # Gemini and OpenAI native compatibility routes are intentionally exposed
+  # without the /api prefix. Keep them on the API upstream instead of allowing
+  # the catch-all Web location to return 405 for valid provider requests.
+  location ~ ^/v1(?:beta)?/ {
+    proxy_http_version 1.1;
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto https;
+    proxy_set_header Connection "";
+    proxy_connect_timeout 2s;
+    proxy_send_timeout 3600s;
+    proxy_read_timeout 3600s;
+    proxy_request_buffering off;
+    proxy_buffering off;
+    proxy_next_upstream error timeout http_502 http_503 http_504;
+    proxy_next_upstream_tries 2;
+    proxy_pass http://easyai_gateway_api;
+  }
+
   location /gateway-api/ {
     proxy_http_version 1.1;
     proxy_set_header Host $host;