fix: World reloading issue for barrels

[Thorinwasher]

Fixes #197

Currently just includes debug messages.

[Minecraft0122]

I traced #197 beyond the debug logging in this draft. The world listener exists but is never registered, and once registered the current full-save path would delete persisted barrels for worlds that are not loaded.

#223 contains the actual fix: listener registration, reload on world load, save/unregister on unload, preservation of unloaded-world records during autosave, explicit deletion for genuinely destroyed barrels, and the Folia no-event path. It also builds successfully against current master.

Since this PR only adds diagnostics and is now conflicting, I recommend superseding it with #223.