Spawn Management

Added:

• /spawnmanager setexactspawn <x> <y> <z> — Sets the world spawn to a precise block with zero random scatter. Supports relative coordinates (~ ~ ~) with full tab-completion.
• /spawnmanager setspawnradius <blocks> — Sets the radius of the protection zone around spawn (default: 32 blocks). Use 0 to disable entirely.
• Block protection — Non-op players cannot break blocks inside the protection radius.
• Damage immunity — Players inside the zone take no damage from any source.
• Zone exit notification — Players receive a message when they walk outside the protected area.

Fixed:

• Overworld only — Protection applies exclusively to the Overworld. Nether and End are unaffected.
• Persistent config — Radius is saved to config/spawnmanager.json and survives restarts. No manual editing needed.
• Server-side only — Players do not need the mod installed on their client.