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/PlayerFaction/Api/GetPlayerFactionHandler.cs

@@ -4,21 +4,21 @@ namespace SpaceGame.Api.PlayerFaction.Api;
 
 public sealed class GetPlayerFactionHandler(WorldService worldService) : EndpointWithoutRequest<PlayerFactionSnapshot>
 {
-  public override void Configure()
-  {
-    Get("/api/player-faction");
-    AllowAnonymous();
-  }
-
-  public override async Task HandleAsync(CancellationToken cancellationToken)
-  {
-    var snapshot = worldService.GetPlayerFaction();
-    if (snapshot is null)
+    public override void Configure()
     {
-      await SendNotFoundAsync(cancellationToken);
-      return;
+        Get("/api/player-faction");
+        AllowAnonymous();
     }
 
-    await SendOkAsync(snapshot, cancellationToken);
-  }
+    public override async Task HandleAsync(CancellationToken cancellationToken)
+    {
+        var snapshot = worldService.GetPlayerFaction();
+        if (snapshot is null)
+        {
+            await SendNotFoundAsync(cancellationToken);
+            return;
+        }
+
+        await SendOkAsync(snapshot, cancellationToken);
+    }
 }