Refactor world bootstrap and allow empty startup worlds

apps/backend/Universe/Simulation/TimeService.cs

@@ -0,0 +1,23 @@
+using Microsoft.Extensions.Options;
+
+namespace SpaceGame.Api.Universe.Simulation;
+
+public sealed class TimeService(
+  IBalanceService balance,
+  IOptions<OrbitalSimulationOptions> orbitalSimulation) : ITimeService
+{
+    public int TickIntervalMs => 200;
+    public TimeSpan TickInterval => TimeSpan.FromMilliseconds(TickIntervalMs);
+    public float TickDeltaSeconds => TickIntervalMs / 1000f;
+    public double SimulatedSecondsPerRealSecond => orbitalSimulation.Value.SimulatedSecondsPerRealSecond;
+
+    public DateTimeOffset UtcNow() => DateTimeOffset.UtcNow;
+
+    public float ScaleSimulationDelta(float realDeltaSeconds) =>
+      realDeltaSeconds * MathF.Max(balance.SimulationSpeedMultiplier, 0.01f);
+
+    public double ScaleOrbitalDelta(float simulationDeltaSeconds) =>
+      simulationDeltaSeconds * SimulatedSecondsPerRealSecond;
+
+    public double CreateInitialOrbitalTimeSeconds(int seed) => seed * 97d;
+}