chore: add .editorconfig and consistent formatting for backend projects

Adds an `.editorconfig` file with C# and project-specific conventions. Applies consistent indentation and formatting across backend handlers, runtime models, and AI services.

apps/backend/Universe/Simulation/WorldGenerationOptions.cs

@@ -2,7 +2,7 @@ namespace SpaceGame.Api.Universe.Simulation;
 
 public sealed class WorldGenerationOptions
 {
-  public int TargetSystemCount { get; init; }
-  public int AiControllerFactionCount { get; init; }
-  public bool GeneratePlayerFaction { get; init; }
+    public int TargetSystemCount { get; init; }
+    public int AiControllerFactionCount { get; init; }
+    public bool GeneratePlayerFaction { get; init; }
 }