feat: production chain

apps/backend/Contracts/WorldContracts.World.cs

@@ -5,6 +5,8 @@ public sealed record WorldSnapshot(
   int Seed,
   long Sequence,
   int TickIntervalMs,
+  double OrbitalTimeSeconds,
+  OrbitalSimulationSnapshot OrbitalSimulation,
   DateTimeOffset GeneratedAtUtc,
   IReadOnlyList<SystemSnapshot> Systems,
   IReadOnlyList<SpatialNodeSnapshot> SpatialNodes,
@@ -21,6 +23,8 @@ public sealed record WorldSnapshot(
 public sealed record WorldDelta(
   long Sequence,
   int TickIntervalMs,
+  double OrbitalTimeSeconds,
+  OrbitalSimulationSnapshot OrbitalSimulation,
   DateTimeOffset GeneratedAtUtc,
   bool RequiresSnapshotRefresh,
   IReadOnlyList<SimulationEventRecord> Events,
@@ -51,3 +55,6 @@ public sealed record ObserverScope(
   string ScopeKind,
   string? SystemId = null,
   string? BubbleId = null);
+
+public sealed record OrbitalSimulationSnapshot(
+  double SimulatedSecondsPerRealSecond);