fix: fix CI workflow failures for Arch and Alpine package builds

Move checkout before setup-go in Arch workflow so src/go.mod exists,
and remove unsupported --platform container option from Alpine workflow.

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

.gitea/workflows/apk-publish.yml

@@ -10,7 +10,6 @@ jobs:
       - ubuntu-24.04
     container:
       image: alpine:latest
-      options: --platform linux/amd64
     strategy:
       matrix:
         include:

.gitea/workflows/arch-publish.yml

@@ -19,14 +19,14 @@ jobs:
       - name: Install build dependencies
         run: sudo apt-get update -qq && sudo apt-get install -y --no-install-recommends zstd curl
 
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
           go-version-file: src/go.mod
 
-      - name: Checkout repository
-        uses: actions/checkout@v4
-
       - name: Build binary
         run: |
           cd src