修复外部生成任务大载荷导致的内存膨胀

阻止图片编辑器将 Data URL 和超限 JSON 写入生成任务，复用 objectKey 等轻量引用
新增外部生成任务摘要投影与分批 payload 压缩回填流程，避免正式列表读取大字段
收紧 SpacetimeDB 发布为永不删数据并移除 Jenkins 普通清库入口，补齐维护窗口门禁
更新生成绑定、运维文档和回归测试，并完成生产数据副本迁移与压缩验证

package.json

@@ -17,6 +17,7 @@
     "admin-web:typecheck": "node scripts/admin-web-build.mjs typecheck",
     "admin-web:preview": "npm --prefix apps/admin-web run preview --",
     "spacetime:generate": "node scripts/generate-spacetime-bindings.mjs",
+    "spacetime:external-generation:maintain": "node scripts/spacetime-maintain-external-generation-jobs.mjs",
     "check:api-server-env": "node scripts/check-api-server-env.mjs",
     "check:spacetime-runtime-access": "node scripts/check-spacetime-runtime-access.mjs",
     "deploy:rust:remote": "node scripts/run-bash-script.mjs scripts/deploy-rust-remote.sh",