feat(docker): 切换无头浏览器模式，新增 beta 镜像构建

- browser_captcha_personal 改为 headless 模式
- Dockerfile.headed 去掉 xvfb/fluxbox 虚拟显示器依赖
- 新增 beta 分支 CI，推送 ghcr.io flow2api:beta 镜像
- .gitignore 忽略测试文件

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

.github/workflows/docker-publish-beta.yml

@@ -0,0 +1,55 @@
+name: Build and Push Beta Docker Image
+
+on:
+  push:
+    branches:
+      - beta
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push-beta:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout repository
+        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
+
+      - name: Log in to Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=raw,value=beta
+
+      - name: Build and push Docker image (beta)
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: Dockerfile.headed
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha,scope=beta
+          cache-to: type=gha,mode=max,scope=beta