feat: start-at-login is a Settings switch, off by default (v2.5.0)

- Settings → About → "Start AgentHub automatically" (AutostartSettings.tsx,
  GET/PUT /api/settings/autostart, server/lib/autostart.js). The switch is
  the systemd --user unit's / LaunchAgent's enabled state: on writes a unit
  for the running server when none exists and enables it, off disables it;
  neither starts or stops the server. A foreign unit is never touched
  (409 EFOREIGN)
- The plugin bootstrap no longer installs a unit on every install: it
  installs or starts one only while the user has it enabled, and a rewrite
  keeps the enabled state (writeUserService({ enable })). An install that
  already had the unit enabled stays on. A stale-but-enabled unit beside a
  live detached server is repointed, no longer started onto the bound port
- unitIsEnabled / setUnitEnabled in systemd-service.js and launchd-service.js

Also:
- fix(workspace): status bar no longer covers the chat box below md (#61)

client/src/lib/api.ts

@@ -1114,6 +1114,18 @@ export const api = {
       /** DELETE /api/settings/codex-hooks — AgentHub's own hooks only */
       remove: () => request<CodexHooksStatus>("/settings/codex-hooks", { method: "DELETE" }),
     },
+    /** Start the dashboard at boot/login (systemd `--user` / LaunchAgent) — off
+     *  by default; a change never starts or stops the running server. */
+    autostart: {
+      /** GET /api/settings/autostart */
+      get: () => request<AutostartStatus>("/settings/autostart"),
+      /** PUT /api/settings/autostart */
+      set: (enabled: boolean) =>
+        request<AutostartStatus>("/settings/autostart", {
+          method: "PUT",
+          body: JSON.stringify({ enabled }),
+        }),
+    },
     /** Opt-in secret redaction of stored payloads and the folders whose hooks
      *  are dropped (`server/lib/privacy.js`). */
     privacy: {
@@ -4334,6 +4346,16 @@ export interface RemoteSourceInput {
   enabled?: boolean;
 }
 
+/** GET /api/settings/autostart. `available` false: no systemd `--user` /
+ *  launchd GUI session here; `foreign`: a unit named agenthub AgentHub did not
+ *  write, which it never touches. */
+export interface AutostartStatus {
+  available: boolean;
+  kind: "systemd" | "launchd";
+  enabled: boolean;
+  foreign: boolean;
+}
+
 /** GET /api/settings/privacy. A field the environment set is `env_owned`
  *  and cannot be saved from the dashboard. */
 export interface PrivacySettings {