feat: 迁入 MiGu.Server、平台前端与车辆列表 reflection 回退

从 Simple-FR 拆出 Platform.Server 并重命名为 MiGu.Server；frontends 源码与构建脚本迁入本仓库。地图监控在 projection/cars 失败或为空时回退 reflection 车辆列表；Simple 仓库已移除旧 Platform.Server。

Co-authored-by: Cursor <cursoragent@cursor.com>

MiGu.Server/wwwroot/assets/el-card-BAyktVMS.css

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+.el-card{--el-card-border-color:var(--el-border-color-light);--el-card-border-radius:4px;--el-card-padding:20px;--el-card-bg-color:var(--el-fill-color-blank);border-radius:var(--el-card-border-radius);border:1px solid var(--el-card-border-color);background-color:var(--el-card-bg-color);color:var(--el-text-color-primary);transition:var(--el-transition-duration);flex-direction:column;display:flex;overflow:hidden}.el-card.is-always-shadow,.el-card.is-hover-shadow:hover,.el-card.is-hover-shadow:focus{box-shadow:var(--el-box-shadow-light)}.el-card__header{padding:calc(var(--el-card-padding) - 2px) var(--el-card-padding);border-bottom:1px solid var(--el-card-border-color);box-sizing:border-box}.el-card__body{padding:var(--el-card-padding);flex-grow:1;overflow:auto}.el-card__footer{padding:calc(var(--el-card-padding) - 2px) var(--el-card-padding);border-top:1px solid var(--el-card-border-color);box-sizing:border-box}