KinglyBosses 5.0.0-DEV-9

Added

• Added a shared attribute utility to handle Minecraft attribute keys consistently across boss spawning flows.

Changed

• Updated plugin API target from Minecraft/Paper 1.19 to 1.21.
• Plugin version is now pulled from Maven during build.
• Refactored boss attribute handling in spawn, respawn, command spawn, ID-based spawn, and invoked attack mobs.

Fixed

• Improved compatibility with newer Paper/Minecraft 1.21 attribute names.
• Added fallback support for legacy generic.* attribute keys.
• Reduced duplicated attribute registry logic across different boss spawn paths.

Technical

• Verified Java 21 compilation.
• Built test jar: kinglybosses-5.0.0-DEV-9.jar.