Implement Equals for ApcBoundInterfaceState (#27965)

* Implement Equals for ApcBoundInterfaceState

Saves a lot on bandwidth. Also made it round to the nearest 5.

* Also this

Content.Server/Power/EntitySystems/ApcSystem.cs

@@ -8,6 +8,7 @@ using Content.Shared.APC;
 using Content.Shared.Emag.Components;
 using Content.Shared.Emag.Systems;
 using Content.Shared.Popups;
+using Content.Shared.Rounding;
 using Robust.Server.GameObjects;
 using Robust.Shared.Audio;
 using Robust.Shared.Audio.Systems;
@@ -147,10 +148,14 @@ public sealed class ApcSystem : EntitySystem
             return;
 
         var battery = netBat.NetworkBattery;
+        const int ChargeAccuracy = 5;
+
+        // TODO: Fix ContentHelpers or make a new one coz this is cooked.
+        var charge = ContentHelpers.RoundToNearestLevels(battery.CurrentStorage / battery.Capacity, 1.0, 100 / ChargeAccuracy) / 100f * ChargeAccuracy;
 
         var state = new ApcBoundInterfaceState(apc.MainBreakerEnabled, apc.HasAccess,
             (int) MathF.Ceiling(battery.CurrentSupply), apc.LastExternalState,
-            battery.CurrentStorage / battery.Capacity);
+            charge);
 
         _ui.SetUiState((uid, ui), ApcUiKey.Key, state);
     }