refactor: 删除未使用的 Models.SimEvent，消除 SimEvent 重名

- 删除 Models/SimEvent.cs（DB表定义，无人读写）
- 删除 DatabaseManager 中 CreateTable<SimEvent> 和 CreateIndex
- DatabaseManagerTests 表数量 13→12

src/CounterDrone.Core/DatabaseManager.cs

@@ -72,14 +72,12 @@ namespace CounterDrone.Core
             db.CreateTable<Waypoint>();
             db.CreateTable<Group>();
             db.CreateTable<SimulationReport>();
-            db.CreateTable<SimEvent>();
 
             db.CreateIndex("SimTask", "TaskNumber");
             db.CreateIndex("ControlZone", "TaskId");
             db.CreateIndex("TargetConfig", "TaskId");
             db.CreateIndex("EquipmentDeployment", "TaskId");
             db.CreateIndex("Waypoint", "TaskId");
-            db.CreateIndex("SimEvent", "TaskId");
             db.CreateIndex("SimulationReport", "TaskId");
         }
     }

src/CounterDrone.Core/Models/SimEvent.cs

@@ -1,28 +0,0 @@
-using System;
-using SQLite;
-
-namespace CounterDrone.Core.Models
-{
-    /// <summary>仿真事件（数据库记录）</summary>
-    [Table("SimEvent")]
-    public class SimEvent
-    {
-        [PrimaryKey]
-        public string Id { get; set; } = Guid.NewGuid().ToString();
-
-        [Indexed]
-        public string TaskId { get; set; } = string.Empty;
-
-        public double OccurredAt { get; set; }
-
-        public int EventType { get; set; }
-
-        public string SourceId { get; set; } = string.Empty;
-
-        public string TargetId { get; set; } = string.Empty;
-
-        public string DataJson { get; set; } = "{}";
-
-        public string Description { get; set; } = string.Empty;
-    }
-}

test/unit/CounterDrone.Core.Tests/DatabaseManagerTests.cs

@@ -31,13 +31,13 @@ namespace CounterDrone.Core.Tests
         {
             var db = _dbManager.OpenMainDb();
 
-            // 验证所有 13 张表存在
+            // 验证所有 12 张表存在
             var tables = new[]
             {
                 "ModelInfo", "AmmunitionSpec", "SimTask", "CombatScene",
                 "ControlZone", "TargetConfig", "EquipmentDeployment",
                 "CloudDispersal", "RoutePlan", "Waypoint", "Group",
-                "SimulationReport", "SimEvent"
+                "SimulationReport"
             };
 
             foreach (var table in tables)