fix: persist consumed research costs to NBT for restart-safe refunds

consumedCosts and consumedFluidCost were in-memory-only snapshots; a
server restart during active research would null them out, making
cancel give no refund. Both fields are now serialized in saveAdditional
and restored in loadAdditional so refunds survive chunk reloads and
server restarts.

Author: MrSilly07

src/main/java/com/researchcube/block/ResearchTableBlockEntity.java

@@ -47,6 +47,7 @@
 import software.bernie.geckolib.animation.*;
 import software.bernie.geckolib.util.GeckoLibUtil;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
 
@@ -627,6 +628,23 @@ protected void saveAdditional(CompoundTag tag, HolderLookup.Provider registries)
             if (researchKey != null) {
                 tag.putString("ResearchKey", researchKey);
             }
+            // Persist consumed costs so refunds survive server restarts
+            if (consumedCosts != null) {
+                ListTag costList = new ListTag();
+                for (ItemCost cost : consumedCosts) {
+                    CompoundTag costTag = new CompoundTag();
+                    costTag.putString("Item", cost.itemId().toString());
+                    costTag.putInt("Count", cost.count());
+                    costList.add(costTag);
+                }
+                tag.put("ConsumedCosts", costList);
+            }
+            if (consumedFluidCost != null) {
+                CompoundTag fluidCostTag = new CompoundTag();
+                fluidCostTag.putString("Fluid", consumedFluidCost.fluidId().toString());
+                fluidCostTag.putInt("Amount", consumedFluidCost.amount());
+                tag.put("ConsumedFluidCost", fluidCostTag);
+            }
         }
     }
 
@@ -653,9 +671,30 @@ protected void loadAdditional(CompoundTag tag, HolderLookup.Provider registries)
             startTime = -1;
             researchKey = null;
         }
-        // consumedCosts/consumedFluidCost are not persisted — on reload, cancel will not refund
-        consumedCosts = null;
-        consumedFluidCost = null;
+        // Restore consumed costs for refund support across restarts
+        if (tag.contains("ConsumedCosts", Tag.TAG_LIST)) {
+            ListTag costList = tag.getList("ConsumedCosts", Tag.TAG_COMPOUND);
+            List<ItemCost> costs = new ArrayList<>();
+            for (int i = 0; i < costList.size(); i++) {
+                CompoundTag costTag = costList.getCompound(i);
+                costs.add(new ItemCost(
+                        ResourceLocation.parse(costTag.getString("Item")),
+                        costTag.getInt("Count")
+                ));
+            }
+            consumedCosts = costs;
+        } else {
+            consumedCosts = null;
+        }
+        if (tag.contains("ConsumedFluidCost", Tag.TAG_COMPOUND)) {
+            CompoundTag fluidCostTag = tag.getCompound("ConsumedFluidCost");
+            consumedFluidCost = new FluidCost(
+                    ResourceLocation.parse(fluidCostTag.getString("Fluid")),
+                    fluidCostTag.getInt("Amount")
+            );
+        } else {
+            consumedFluidCost = null;
+        }
     }
 
     // ── Client Sync ──