VelKoth

feat: enhance scheduling system, PlaceholderAPI, and command parsing

• Implemented dynamic /koth schedule group (add, list, remove)
• Fixed command parsing ambiguity for times with colons (HH:mm)
• Added tab completion for day/time in schedule commands
• Improved placeholder formatting for next event times (00d 00h 00m 00s)
• Bumped version to 1.0.3 and updated README.md
• Refactored SchedulerManager for thread-safe dynamic task management