feat(updates): auto-apply and self-restart on new dashboard versions

Adds POST /api/updates/apply (pull, rebuild, restart) plus an "Update now"
button and hourly auto-check in the UI, for checkouts that are safely
fast-forwardable. Reintroduces self-restart (previously removed in edc25ca
for cross-environment reliability concerns) per explicit user request.

server/lib/self-restart.js

@@ -0,0 +1,32 @@
+/**
+ * @file Triggers the one self-restart path this dashboard has: after
+ * `POST /api/updates/apply` fast-forwards and rebuilds the checkout, the
+ * running process needs to relaunch itself on the new code. Reuses the
+ * existing SIGTERM graceful-shutdown path in `server/index.js` (closes
+ * websockets, drains the HTTP server, closes the DB) instead of duplicating
+ * it, and hands the "wait for the old PID to actually die, then spawn the
+ * replacement" job to a detached helper script — the dying process can't do
+ * that itself without racing its own replacement for the port.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const path = require("path");
+const { spawn } = require("child_process");
+
+/**
+ * @param {string} [root] repo root the helper should run from.
+ */
+function scheduleRestart(root = path.join(__dirname, "..", "..")) {
+  const helperPath = path.join(root, "scripts", "restart-helper.js");
+  const entry = process.argv[1] || path.join(root, "server", "index.js");
+  const helper = spawn(process.execPath, [helperPath, String(process.pid), entry], {
+    cwd: root,
+    detached: true,
+    stdio: "ignore",
+    env: process.env,
+  });
+  helper.unref();
+  process.kill(process.pid, "SIGTERM");
+}
+
+module.exports = { scheduleRestart };