release: bump version to 5.1.1 and fix dns download issue

add --async-dns=false aria2 parameter to all download jobs to fix potential dns resolution failures during package download

electron/main/backend/install-manager.ts

@@ -390,6 +390,7 @@ async function processNextInQueue() {
       const aria2Args = [
         `--dir=${downloadDir}`,
         "--allow-overwrite=true",
+        "--async-dns=false",
         "--summary-interval=1",
         "--connect-timeout=10",
         "--timeout=15",

electron/main/backend/shared-installer.ts

@@ -89,6 +89,7 @@ export const downloadPackage = async ({
   const aria2Args = [
     `--dir=${downloadDir}`,
     "--allow-overwrite=true",
+    "--async-dns=false",
     "--summary-interval=1",
     "--connect-timeout=10",
     "--timeout=15",