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.

web/shared/api/schema.ts

@@ -1178,6 +1178,23 @@ export interface paths {
         patch?: never;
         trace?: never;
     };
+    "/install/compose/{file}": {
+        parameters: {
+            query?: never;
+            header?: never;
+            path?: never;
+            cookie?: never;
+        };
+        /** The static compose file of agent, probe or backend (agent.yaml, probe.yaml, backend.yaml; same bytes for everyone) */
+        get: operations["install_compose"];
+        put?: never;
+        post?: never;
+        delete?: never;
+        options?: never;
+        head?: never;
+        patch?: never;
+        trace?: never;
+    };
     "/install.ps1": {
         parameters: {
             query?: never;
@@ -1407,6 +1424,14 @@ export interface components {
                 [key: string]: null | number | string;
             };
         };
+        ComposeInstallDto: {
+            env: string;
+            url: string;
+            sha256: string;
+            linux: string;
+            macos: string;
+            windows: string;
+        };
         ConfirmBackendUpdateRequest: {
             /** Format: int64 */
             seq: number | string;
@@ -1459,6 +1484,7 @@ export interface components {
             token: components["schemas"]["JoinTokenDto"];
             plaintext: string;
             install_commands: components["schemas"]["InstallCommandsDto"];
+            compose: components["schemas"]["ComposeInstallDto"];
         };
         DimensionDto: {
             id: string;
@@ -6179,6 +6205,35 @@ export interface operations {
             };
         };
     };
+    install_compose: {
+        parameters: {
+            query?: never;
+            header?: never;
+            path: {
+                file: string;
+            };
+            cookie?: never;
+        };
+        requestBody?: never;
+        responses: {
+            /** @description OK */
+            200: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content?: never;
+            };
+            /** @description Not Found */
+            404: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/problem+json": components["schemas"]["ProblemDto"];
+                };
+            };
+        };
+    };
     install_ps1: {
         parameters: {
             query?: never;

web/shared/api/types.ts

@@ -40,6 +40,7 @@ export type ParamDto = Narrow<S['ParamDto']>
 export type MetricDto = Narrow<S['MetricDto']>
 export type JoinTokenDto = Narrow<S['JoinTokenDto']>
 export type CreatedJoinTokenDto = Narrow<S['CreatedJoinTokenDto']>
+export type ComposeInstallDto = Narrow<S['ComposeInstallDto']>
 export type ApiTokenDto = Narrow<S['ApiTokenDto']>
 export type CreatedApiTokenDto = Narrow<S['CreatedApiTokenDto']>
 export type CapabilityCatalogDto = Narrow<S['CapabilityCatalogDto']>