fix(nginx): /api/auth/ 프록시 추가 — 비밀번호 변경 API 라우팅

change-password.js가 /api/auth/change-password로 요청하는데
기존 /api/ location이 system1-api로 보내서 404 발생.
/api/auth/ location을 /api/ 앞에 추가하여 sso-auth로 프록시.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

system1-factory/web/nginx.conf

@@ -24,6 +24,17 @@ server {
         add_header Cache-Control "public, no-transform";
     }
 
+    # SSO Auth API 프록시 (/api/auth/* → sso-auth)
+    location /api/auth/ {
+        set $upstream http://sso-auth:3000;
+        proxy_pass $upstream$request_uri;
+        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 $scheme;
+    }
+
     # API 프록시 (System 1 API)
     location /api/ {
         set $upstream http://system1-api:3005;