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/Configs/SystemConfig.cs

@@ -0,0 +1,12 @@
+namespace MiGu.Server.Configs;
+
+public record LogPolicy(string Level, int RollDays, int MaxSizeMB);
+public record SecurityPolicy(int JwtExpireMin, bool EnableSwagger, List<string> CorsWhitelist);
+
+public record SystemConfig(int DispatchLoopHz, LogPolicy Log, SecurityPolicy Security)
+{
+    public static SystemConfig Default() => new(
+        DispatchLoopHz: 50,
+        Log: new LogPolicy("info", 7, 256),
+        Security: new SecurityPolicy(1440, false, new List<string> { "http://localhost:5173" }));
+}