CommunityVault

Added safety, backups, compaction fixes, admin tools, and tests

• Prevent shulker duplication/compaction loss: skip compaction for unstackables and remove exact stacks by meta for unstackables.
• Fix zero-cost chest purchases and safe withdrawals (stack into inventory, rollback on no space).
• Add manual compact/status commands (/cvaultcompact, /cvaultstatus) and short search alias /sv; track last backup time.
• Add backup pruning/creation on start/stop; expose health info in status command.
• Harden UI handling (metadata checks, avoid treating arrow items as nav buttons; add nav lore).
• Extend tests for stacking/compaction, fit checks, unstackable handling, and basic round-trip.