New guides added to the species library.

The species library now includes expanded growing and harvesting notes across our core lineup -- written for the same fruiting blocks and spawn sold in the shop, not generic reference material. If you've picked up a block and want the specifics on humidity, fresh air exchange, or when to expect first pins, the Learn section and each species page are the place to start. More guides are in progress, prioritized by whatever questions come in most often -- if there's a gap you keep running into, it's worth flagging.