New: [Occupy Abandoned Buildings] feature. Fixed collapse bugs.

● Added: Zombies no longer spawn within 10m of any player-built structure. Just place a few items inside an abandoned building to fully claim it.

● Fixed scope reticle not showing.

● Fixed building system accidentally causing wall collapse.

● Fixed wooden floor collapsing when placing items on it. Note for old saves: place a new structure on ground, save overwriting the old save, then reload.

● Fixed game freezing for ~3 sec every few minutes (auto-memory cleanup). Increased cleanup interval to 30 min.

● Fixed spike trap hurting crouching players.

● Fixed shotgun infinite reload.

● Fixed excessive zombie mutation level when horde attacks very large bases.

● Greatly reduced looting timer on corpse containers.