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.

backend/tests/MoShiro.Backend.Tests/InstallTests.cs

@@ -48,6 +48,78 @@ public sealed class InstallTests
         Assert.DoesNotContain("<", linux + macos + windows, StringComparison.Ordinal); // 没有要用户自己替换的占位符
     }
 
+    [Theory]
+    [InlineData("agent")]
+    [InlineData("probe")]
+    public async Task ComposeInstall_WritesThePublicValuesToAnEnvFile_AndChecksTheComposeHash(string role)
+    {
+        JsonNode created = await CreateAsync(role);
+        string code = created["plaintext"]!.GetValue<string>();
+        JsonNode compose = created["compose"]!;
+        string env = compose["env"]!.GetValue<string>();
+        string url = compose["url"]!.GetValue<string>();
+        string linux = compose["linux"]!.GetValue<string>();
+
+        Assert.EndsWith($"/install/compose/{role}.yaml", url, StringComparison.Ordinal);
+        Assert.Contains($"MOSHIRO_JOIN={code}", env, StringComparison.Ordinal);
+        Assert.Contains("MOSHIRO_SERVER=", env, StringComparison.Ordinal);
+        Assert.Contains($"/moshiro-{role}", env, StringComparison.Ordinal); // MOSHIRO_IMAGE：仓库和命名空间来自后端的配置，不是写死的
+        Assert.StartsWith($"mkdir -p moshiro-{role} && cd moshiro-{role} && cat > .env <<'EOF'\n", linux, StringComparison.Ordinal);
+        Assert.Contains(env, linux, StringComparison.Ordinal);
+        Assert.Contains("chmod 600 .env", linux, StringComparison.Ordinal);
+        Assert.Contains($"echo \"{compose["sha256"]!.GetValue<string>()}  compose.yaml\" | sha256sum -c -", linux, StringComparison.Ordinal);
+        Assert.EndsWith("podman compose up -d", linux, StringComparison.Ordinal);
+
+        // 面板提供的就是命令里核对的那份
+        using HttpResponseMessage served = await _backend.Anonymous.GetAsync($"/install/compose/{role}.yaml");
+        Assert.Equal(HttpStatusCode.OK, served.StatusCode);
+        Assert.Equal("text/yaml", served.Content.Headers.ContentType?.MediaType);
+        byte[] body = await served.Content.ReadAsByteArrayAsync();
+        Assert.Equal(compose["sha256"]!.GetValue<string>(), Convert.ToHexStringLower(System.Security.Cryptography.SHA256.HashData(body)));
+
+        if (role == "probe")
+        {
+            // Docker Desktop 没有宿主网络：macOS 和 Windows 的 .env 里改成 bridge
+            string macos = compose["macos"]!.GetValue<string>();
+            string windows = compose["windows"]!.GetValue<string>();
+            Assert.Contains("MOSHIRO_NETWORK_MODE=bridge", macos + windows, StringComparison.Ordinal);
+            Assert.Contains("docker compose up -d", macos, StringComparison.Ordinal);
+            Assert.Contains("Get-FileHash compose.yaml", windows, StringComparison.Ordinal);
+        }
+        else
+        {
+            // Agent 需要 Linux 的宿主网络
+            Assert.Equal(string.Empty, compose["macos"]!.GetValue<string>());
+            Assert.Equal(string.Empty, compose["windows"]!.GetValue<string>());
+        }
+    }
+
+    [Theory]
+    [InlineData("agent.yaml")]
+    [InlineData("probe.yaml")]
+    [InlineData("backend.yaml")]
+    public async Task TheComposeFiles_AreStatic_PinNothingToABuild_AndKeepTheNodeHardening(string file)
+    {
+        string body = await _backend.Anonymous.GetStringAsync("/install/compose/" + file);
+
+        Assert.Contains("${MOSHIRO_VERSION:-latest}", body, StringComparison.Ordinal); // 更新就是 pull 加 up，想固定版本在 .env 里写
+        Assert.Contains("read_only: true", body, StringComparison.Ordinal);
+        Assert.Contains("no-new-privileges:true", body, StringComparison.Ordinal);
+        Assert.Contains("- ALL", body, StringComparison.Ordinal); // cap_drop
+        Assert.DoesNotContain("jt_", body, StringComparison.Ordinal); // 没有任何一次性的值
+    }
+
+    [Theory]
+    [InlineData("evil.yaml")]
+    [InlineData("agent")]
+    [InlineData("..%2Finstall.sh")]
+    public async Task OnlyTheThreeComposeFiles_AreServed(string file)
+    {
+        using HttpResponseMessage response = await _backend.Anonymous.GetAsync("/install/compose/" + file);
+
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+
     [Fact]
     public async Task TheScripts_AreStatic_TheSameBytesForEveryone_AndNeedNoCode()
     {