Factory Production Upgrade

Upgrade factories in single-player or multiplayer without placing multiple copies of the same production.

Progression levels: 1x, 2x, 3x, 5x, 10x, 20x, 30x, 40x, 50x, 60x.
Each additional +1x throughput increase costs 5% of the factory's original purchase price.
Storage capacity and discharge speed use the same multiplier, with MP-safe storage synchronization.
Operating costs also scale with throughput, preserving the base cost per produced unit.
Upgrade payments, ownership validation, saving, and level synchronization are all server-authoritative in multiplayer.

Excluded base-game productions: Playground maker hall, wagon builder, and piano manufacture.