Fix firelock lights for hot / pressurized rooms (#15892)

Content.Client/Doors/FirelockSystem.cs

@@ -0,0 +1,27 @@
+using Content.Shared.Doors.Components;
+using Robust.Client.GameObjects;
+
+namespace Content.Client.Doors;
+
+public sealed class FirelockSystem : EntitySystem
+{
+    [Dependency] protected readonly SharedAppearanceSystem AppearanceSystem = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeLocalEvent<FirelockComponent, AppearanceChangeEvent>(OnAppearanceChange);
+    }
+
+    private void OnAppearanceChange(EntityUid uid, FirelockComponent comp, ref AppearanceChangeEvent args)
+    {
+        if (args.Sprite == null)
+            return;
+
+        // Apply the closed lights bool to the sprite
+        bool unlitVisible =
+            (AppearanceSystem.TryGetData<bool>(uid, DoorVisuals.ClosedLights, out var closedLights, args.Component) &&
+             closedLights);
+        args.Sprite.LayerSetVisible(DoorVisualLayers.BaseUnlit, unlitVisible);
+    }
+}