fix: OnDisable + Dispose 替代 OnDestroy + Close，修复 domain reload SQLite 崩溃

OnDisable 在 domain reload 前触发，Dispose() 清理 prepared statements 并调用 GC.SuppressFinalize，阻止 GC finalizer 线程崩溃

src/Unity/Assets/Scripts/Managers/GroupManager.cs

@@ -22,7 +22,7 @@ namespace CounterDrone.Unity
             _service = new GroupService(new GroupRepository(_db));
         }
 
-        void OnDestroy() => _db?.Close();
+        void OnDisable() { _db?.Dispose(); _db = null; }
 
         public Group Create(string name, GroupType type, string desc = "")
             => _service.CreateGroup(name, type, desc);

src/Unity/Assets/Scripts/Managers/ModelManager.cs

@@ -24,7 +24,7 @@ namespace CounterDrone.Unity
             _service = new ModelService(new ModelRepository(_db), _paths);
         }
 
-        void OnDestroy() => _db?.Close();
+        void OnDisable() { _db?.Dispose(); _db = null; }
 
         public ModelInfo Import(string filePath, string name) => _service.ImportModel(filePath, name);
         public void Delete(string id) => _service.DeleteModel(id);

src/Unity/Assets/Scripts/Managers/ReportManager.cs

@@ -22,7 +22,7 @@ namespace CounterDrone.Unity
             _service = new ReportService(_db, _paths);
         }
 
-        void OnDestroy() => _db?.Close();
+        void OnDisable() { _db?.Dispose(); _db = null; }
 
         public SimulationReport Generate(string taskId, TaskFullConfig cfg, List<SimEvent> events, string status, float duration)
             => _service.Generate(taskId, cfg, events, status, duration);

src/Unity/Assets/Scripts/Managers/ScenarioManager.cs

@@ -35,7 +35,7 @@ namespace CounterDrone.Unity
             }
         }
 
-        void OnDestroy() => _db?.Close();
+        void OnDisable() { _db?.Dispose(); _db = null; }
 
         public SimTask CreateTask(string name, string number) => _service.CreateTask(name, number);
         public void DeleteTask(string id) => _service.DeleteTask(id);

src/Unity/Assets/Scripts/Managers/SimulationRunner.cs

@@ -149,7 +149,8 @@ namespace CounterDrone.Unity
         }
 
         public void Stop() => _engine?.Stop();
-        void OnDestroy() { Stop(); _db?.Close(); }
+        void OnDisable() { _db?.Dispose(); _db = null; }
+        void OnDestroy() => Stop();
 
         private void SpawnDroneVisual(DroneEntity drone)
         {