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/settingsSearch.ts

@@ -104,6 +104,12 @@ export const SETTINGS_INDEX: {
     titleKey: "about.title",
     keywords: ["version", "server", "database", "uptime"],
   },
+  {
+    section: "about",
+    titleKey: "autostart.label",
+    keywords: ["autostart", "boot", "login", "systemd", "launchd", "service"],
+    to: "#autostart",
+  },
   {
     section: "appearance",
     titleKey: "sagi.title",