fix: force linux/amd64 platform for Arch container

archlinux:latest has no ARM64 image on Docker Hub.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/arch-publish.yml

@@ -10,6 +10,7 @@ jobs:
       - ubuntu-24.04
     container:
       image: archlinux:latest
+      options: --platform linux/amd64
     steps:
       - name: Install build dependencies
         run: pacman -Syu --noconfirm git nodejs go base-devel curl