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-loading-Dq8WDDkr.css

@@ -0,0 +1 @@
+:root{--el-loading-spinner-size:42px;--el-loading-fullscreen-spinner-size:50px}.el-loading-parent--relative{position:relative!important}.el-loading-parent--hidden{overflow:hidden!important}.el-loading-mask{z-index:2000;background-color:var(--el-mask-color);transition:opacity var(--el-transition-duration);margin:0;position:absolute;inset:0}.el-loading-mask.is-fullscreen{position:fixed}.el-loading-mask.is-fullscreen .el-loading-spinner{margin-top:calc((0px - var(--el-loading-fullscreen-spinner-size)) / 2)}.el-loading-mask.is-fullscreen .el-loading-spinner .circular{height:var(--el-loading-fullscreen-spinner-size);width:var(--el-loading-fullscreen-spinner-size)}.el-loading-spinner{margin-top:calc((0px - var(--el-loading-spinner-size)) / 2);text-align:center;width:100%;position:absolute;top:50%}.el-loading-spinner .el-loading-text{color:var(--el-color-primary);margin:3px 0;font-size:14px}.el-loading-spinner .circular{height:var(--el-loading-spinner-size);width:var(--el-loading-spinner-size);animation:2s linear infinite loading-rotate;display:inline}.el-loading-spinner .path{stroke-dasharray:90 150;stroke-dashoffset:0;stroke-width:2px;stroke:var(--el-color-primary);stroke-linecap:round;animation:1.5s ease-in-out infinite loading-dash}.el-loading-spinner i{color:var(--el-color-primary)}.el-loading-fade-enter-from,.el-loading-fade-leave-to{opacity:0}@keyframes loading-rotate{to{transform:rotate(360deg)}}@keyframes loading-dash{0%{stroke-dasharray:1 200;stroke-dashoffset:0}50%{stroke-dasharray:90 150;stroke-dashoffset:-40px}to{stroke-dasharray:90 150;stroke-dashoffset:-120px}}