ci: 运行环境自愈预置 + 发版任务串行 + 删 ci.yml/暂停备份

- 新增 scripts/ci/provision-{mac,windows}.sh：幂等预置，按 Flutter 版本
  stamp 短路，pipeline 首跑自动 precache + 预热缓存，运行时不再下载 engine
- scripts/ci/_env.sh：抽出共用镜像 env，compile 脚本统一 source
- deploy.yml：build-macos needs build-linux-web，同一 mac runner 串行
  执行，避免排队超时；各 build job 加 Provision 前置步骤
- 删除 .gitea/workflows/ci.yml
- backup.yml：暂停定时备份（保留 workflow_dispatch 手动触发）

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

scripts/ci/provision-windows.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+# provision-windows.sh — idempotent provisioning for the Windows host runner.
+#
+# Pre-warms what compile-windows.sh would download at runtime: Flutter Windows
+# engine artifacts and pub packages. Short-circuits via a stamp file keyed to
+# the installed Flutter version, so repeat runs return immediately.
+set -euo pipefail
+
+SCRIPT_DIR="$(dirname "$0")"
+# shellcheck source=scripts/ci/_env.sh
+. "${SCRIPT_DIR}/_env.sh"
+
+STAMP_DIR="${HOME}/.cache/jiu-ci"
+STAMP="${STAMP_DIR}/provisioned-windows"
+CUR="${STAMP_DIR}/.flutter-version-win.cur"
+mkdir -p "$STAMP_DIR"
+
+# --- detection ---
+if ! command -v flutter >/dev/null 2>&1; then
+  echo "ERROR: flutter not found on PATH. Install Flutter on this runner first." >&2
+  exit 1
+fi
+flutter --version --machine > "$CUR" 2>/dev/null || flutter --version > "$CUR" 2>&1 || true
+
+if [ -s "$STAMP" ] && cmp -s "$STAMP" "$CUR"; then
+  echo "==> provision-windows: already provisioned (Flutter unchanged), skipping."
+  exit 0
+fi
+
+echo "==> provision-windows: not provisioned (or Flutter changed) — running."
+
+# --- warm Flutter Windows engine + pub deps ---
+echo "==> precache Flutter engine (windows)"
+flutter precache --windows
+
+echo "==> flutter pub get (client)"
+(cd "${SCRIPT_DIR}/../../client" && flutter pub get)
+
+# --- mark provisioned ---
+cp "$CUR" "$STAMP"
+echo "==> provision-windows: done."
+flutter --version | head -1