ci: 新增仅构建 Windows 的 workflow (build-windows.yml)

手动 workflow_dispatch 或推 winbuild* tag 触发，复用 provision/compile-windows.sh，
产物经 upload-artifact 传到 Forgejo，不触发完整 deploy。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitea/workflows/build-windows.yml

@@ -0,0 +1,42 @@
+name: Build Windows Only
+
+# 仅构建 Windows 桌面版（不触发完整 deploy）。
+# 触发方式：
+#   - 手动 workflow_dispatch（可填 ver）
+#   - 推送 winbuild* 轻量 tag（如 winbuild1），不与 deploy.yml 的 v* tag 冲突
+on:
+  workflow_dispatch:
+    inputs:
+      ver:
+        description: '版本号 (如 v1.0.4)'
+        required: false
+        default: 'v1.0.4'
+        type: string
+  push:
+    tags:
+      - 'winbuild*'
+
+jobs:
+  build-windows:
+    runs-on: windows
+    env:
+      GOPROXY: https://goproxy.cn,direct
+      PUB_HOSTED_URL: https://pub.flutter-io.cn
+      FLUTTER_STORAGE_BASE_URL: https://storage.flutter-io.cn
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Provision (idempotent — auto-runs if host not initialized)
+        shell: bash
+        run: sh scripts/ci/provision-windows.sh
+
+      - name: Compile (Flutter Windows)
+        shell: bash
+        run: sh scripts/ci/compile-windows.sh "${{ inputs.ver || 'v1.0.4' }}"
+
+      - name: Upload windows artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: jiu-windows
+          path: dist/