fix(ci): simplify workflow to debug OAuth token timeout

- remove QEMU setup (amd64-only build, not needed)
- remove registry build cache (buildkit cache uses separate auth flow,
  suspected cause of HTTP fallback in /v2/token request)
- switch gitea.actor/event_name to github.actor/event_name for
  broader action compatibility

Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>

.gitea/workflows/build-and-push.yml

@@ -28,9 +28,6 @@ jobs:
       - name: Checkout source
         uses: actions/checkout@v4
 
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
-
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
@@ -42,7 +39,7 @@ jobs:
           # 推荐做法：到 Gitea「用户设置 → 应用 → 生成 Access Token」
           # 勾选 write:package 权限，将值存为仓库 Secret 名为 REGISTRY_TOKEN
           # 注意：Gitea 保留 GITEA_ 前缀，secret 不能以 GITEA_ 开头
-          username: ${{ gitea.actor }}
+          username: ${{ github.actor }}
           password: ${{ secrets.REGISTRY_TOKEN }}
 
       - name: Compute image tags & labels
@@ -61,7 +58,7 @@ jobs:
             # 默认分支自动打 latest
             type=raw,value=latest,enable={{is_default_branch}}
             # 手动触发若提供了 tag，附加这个 tag
-            type=raw,value=${{ inputs.tag }},enable=${{ gitea.event_name == 'workflow_dispatch' && inputs.tag != '' }}
+            type=raw,value=${{ inputs.tag }},enable=${{ github.event_name == 'workflow_dispatch' && inputs.tag != '' }}
 
       - name: Build and push image
         uses: docker/build-push-action@v5
@@ -71,10 +68,6 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-          # 使用 registry 作为构建缓存，多次构建可显著加速
-          # 若你的 Gitea 版本不支持 cache manifest，可注释掉这两行
-          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache
-          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache,mode=max
 
       - name: Print built tags
         run: |