craftable quality buildings

Adds a furniture crafting spot, so quality buildings can be crafted and managed as
workbench bills — e.g. "keep 5 masterwork beds".

Covers ALL 35 vanilla quality furniture pieces.

Recommended alongside Build From Storage and workbench-management mods.
This does not change game balance; it only removes micromanagement. Work type and
priority, work speed, XP gain and unlock conditions all stay identical to building the
same item directly from the architect menu.

Known issue: vanilla uses different work-amount designs for building and crafting, so
some materials cannot be fully matched — crafting small-workload furniture out of stone
and other hard materials may be somewhat faster.

Planned:
1. A version that automatically adapts to quality furniture added by other mods.
2. Expanding the mod to all minifiable buildings, if there is demand.