feat: Adds Endless Decanter of Water and Water Elemental acquisition (#2371)

## Summary

- Adds the Endless Decanter of Water (introduced in Publish 66.2 / SA era)
- Players throw a full Pitcher of Water at a Water Elemental for a 10% chance to receive the decanter; the pitcher is always destroyed on impact
- Each Water Elemental can only yield one decanter; the state is persisted and previously saved elementals are migrated to the new serialization version
- The decanter auto-refills from a linked water trough when the owner empties it within 10 tiles of the stored trough location
- Linking stores a Point3D + Map snapshot, supporting both static tile troughs and addon troughs
- The decanter is blessed and displays Linked/Unlinked status in its tooltip

Projects/UOContent/Migrations/Server.Items.EndlessDecanter.v0.json

@@ -0,0 +1,30 @@
+{
+  "version": 0,
+  "type": "Server.Items.EndlessDecanter",
+  "properties": [
+    {
+      "name": "Linked",
+      "type": "bool",
+      "rule": "PrimitiveTypeMigrationRule",
+      "ruleArguments": [
+        ""
+      ]
+    },
+    {
+      "name": "LinkLocation",
+      "type": "Server.Point3D",
+      "rule": "PrimitiveUOTypeMigrationRule",
+      "ruleArguments": [
+        "Point3D"
+      ]
+    },
+    {
+      "name": "LinkMap",
+      "type": "Server.Map",
+      "rule": "PrimitiveUOTypeMigrationRule",
+      "ruleArguments": [
+        "Map"
+      ]
+    }
+  ]
+}