feat(api): 补齐资源分发服务入口

新增 bat-api 资源 bootstrap/分发 HTTP 服务、RPC release 发现、CDN path 分发、launcher 资源引导兼容、控制面中间件、OpenAPI 和 systemd 模板。

同步 Go 边界文档，明确 Rust bat 是资源生产者和同步运维入口，Go bat-api 是只读 bootstrap/分发服务，试验 Go CLI 产物为 bin/bat-go。

验证：未运行新命令；本轮已按要求停止重复构建/测试。

web/README.md

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+# Reserved empty directory
+
+This path is a monorepo placeholder and is **not implemented**.
+Do not treat it as a finished module. See `docs/reports/GO_STATUS.md`.

web/admin/README.md

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+# bat-api Admin Panel
+
+This directory is reserved for the future player-facing `bat-api` management
+panel. The current backend exposes a protected placeholder at `GET /admin/`
+that returns JSON links for health, readiness, bootstrap, release, resources,
+and OpenAPI.
+
+The production panel must reuse the same HTTP authentication, rate limiting,
+access logging, reverse-proxy handling, and no-store dynamic response policy as
+the resource API. Static frontend assets are not implemented yet.

web/shared/README.md

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+# Reserved empty directory
+
+Placeholder only. **Not implemented.** See `docs/reports/GO_STATUS.md`.