Fix Nether portal target coordinates

[Parham125]

Summary

• Preserve scaled portal target coordinates as a Vec3 when firing Bukkit portal events.
• Use the computed portal search radius for PlayerPortalEvent instead of always passing 128.
• Re-read the target world border after plugins can change the portal destination world.

Testing

• Built successfully in fork GitHub Actions: https://github.com/Parham125/Arclight/actions/runs/25250674706
• Verified on a test server that Overworld to Nether portal coordinates no longer route to 0,0.