fix: 消除 JWT/签名密钥源码硬编码，全部改为环境变量注入

- JwtProperties.adminSecret/appSecret 默认值从 dev 密钥改为空字符串
- MediaProperties.signatureSecret 默认值从 dev 密钥改为空字符串
- app-api/admin-api application.yml 三处密钥回退值均改为空
- docker-compose.yml CORS_ALLOWED_ORIGINS 追加 ymb-site 3007 端口白名单
- .gitignore 追加 *.secrets.env / SSL 证书 / nginx 部署目录忽略规则

fruitshorts-admin-api/src/main/resources/application.yml

@@ -57,14 +57,14 @@ fruitshorts:
     public-prefix: /files
     chunk-size: 5242880
     max-file-size: 2147483648
-    signature-secret: ${MEDIA_SIGNATURE_SECRET:fruitshorts-media-dev-secret-change-me-in-production-32b}
+    signature-secret: ${MEDIA_SIGNATURE_SECRET:}
     signature-required: ${MEDIA_SIGNATURE_REQUIRED:false}
     signature-ttl-minutes: 15
   jwt:
-    # 双密钥都要外置：只配 admin 而漏配 app，生产会静默用 dev 默认值（prod fail-fast 会拦住）
-    admin-secret: ${JWT_ADMIN_SECRET:fruitshorts-admin-dev-secret-change-me-in-production-32b}
+    # ⚠️ 所有环境必须注入 JWT_ADMIN_SECRET / JWT_APP_SECRET，不设任何代码级默认值
+    admin-secret: ${JWT_ADMIN_SECRET:}
     admin-ttl-hours: 12
-    app-secret: ${JWT_APP_SECRET:fruitshorts-app-dev-secret-change-me-in-production-32bytes}
+    app-secret: ${JWT_APP_SECRET:}
     app-access-ttl-minutes: 120
     app-refresh-ttl-days: 30
   cors: