fix update spawn error handling and reset flag

src/server/api/system.ts

@@ -304,9 +304,16 @@ router.get('/update', async c => {
 router.post('/update', c => {
   if (isUpdating) return c.json({ ok: false, error: 'update already in progress' }, 409)
   isUpdating = true
+  try {
     const script = join(projectRoot, 'install/install.sh')
-  Bun.spawn(['bash', script], { cwd: projectRoot, stdout: 'ignore', stderr: 'ignore' })
+    const proc = Bun.spawn(['bash', script], { cwd: projectRoot, stdout: 'ignore', stderr: 'ignore' })
+    proc.exited.then(code => { if (code !== 0) isUpdating = false })
+      .catch(() => { isUpdating = false })
     return c.json({ ok: true })
+  } catch {
+    isUpdating = false
+    return c.json({ ok: false, error: 'failed to start update' }, 500)
+  }
 })
 
 export default router