feat: install nodes and the backend from a static compose file; remove dead code [CI]

Agent, Probe and Backend now start from one static compose.yaml plus a local
.env: the panel (or the release assets, for the very first Backend) provides
the file, the panel's command writes the public values into .env, checks the
file's SHA-256 and runs compose up. Updating is compose pull && compose up -d.
The image is chosen by the CI channel (:latest, or MOSHIRO_VERSION in .env),
not by the panel; the previous one-line script stays as a fallback.

- packaging/compose/{agent,probe,backend}/compose.yaml are the single source,
  embedded in the Backend and served at /install/compose/{file}; the root
  compose.yaml moved there. Releases also carry them and list them in the
  signed SHA256SUMS.
- The container entrypoint defaults the node name to the host name.
- Join token creation returns a compose block (.env, url, hash, per-platform
  commands); the admin dialog leads with it.
- Remove code with no references (HotLayer members, LiveHub.SubscriberCount,
  QueryService.ParseParams, ReleaseService.Forget, a few constants) and reduce
  the install-code lookup to the role it is for.

packaging/compose/agent/compose.yaml

@@ -1,9 +1,15 @@
-# Docker 和 rootless/rootful Podman 共用。配置、身份和缓存保存在命名 volume 中。
-# docker compose up -d / podman compose up -d（Podman 以普通用户执行即可 rootless）。
-# 首次注册、配置导入和自动更新见 docs/ops/deployment.md。
+# MoShiro Agent（Linux，需要宿主网络）。Docker 和 rootless/rootful Podman 共用。
+#
+# 用法（面板「添加 Agent」会给出带好参数的 .env 内容）：
+#   mkdir moshiro-agent && cd moshiro-agent
+#   把面板给的 .env 内容存成 .env，再下载本文件为 compose.yaml
+#   podman compose up -d            # Docker 用 docker compose
+# 更新：podman compose pull && podman compose up -d      （身份和配置在命名卷里，不会动）
+# 固定版本：在 .env 里写 MOSHIRO_VERSION=0.3.3；想要更严，写成 MOSHIRO_VERSION=0.3.3@sha256:<digest>。
+# 说明见 docs/ops/deployment.md。
 services:
   agent:
-    image: ${MOSHIRO_IMAGE:-registry.oeo.one/moshiro/moshiro-agent}:${MOSHIRO_VERSION:-0.1.1}
+    image: ${MOSHIRO_IMAGE:-registry.oeo.one/moshiro/moshiro-agent}:${MOSHIRO_VERSION:-latest}
     container_name: moshiro-agent
     restart: unless-stopped
     init: true
@@ -18,6 +24,13 @@ services:
       - /sys:/host/sys:ro
       - /:/host/root:ro
     environment:
+      # 只在第一次启动时用来注册（身份写进 agent-config 卷之后，.env 里的 MOSHIRO_JOIN 就可以删掉）
+      MOSHIRO_SERVER: ${MOSHIRO_SERVER:-}
+      MOSHIRO_JOIN: ${MOSHIRO_JOIN:-}
+      MOSHIRO_NAME: ${MOSHIRO_NAME:-}
+      MOSHIRO_GENESIS: ${MOSHIRO_GENESIS:-}
+      MOSHIRO_CONTROLLERS: ${MOSHIRO_CONTROLLERS:-}
+      MOSHIRO_ALLOW_NO_OWNER: ${MOSHIRO_ALLOW_NO_OWNER:-}
       MOSHIRO_NETWORK_SCOPE: host
       HOST_PROC: /host/proc
       HOST_SYS: /host/sys