Greenhouse improvements: bigger sizes, growth speed and qual

[Avalon_N7]

Hi!

The Greenhouse (2022-09-20) is rarely used. The issue is not the cost itself, but that the cost isn't justified by what it gives back: 10 metal bars, 15 glass panes, boards, blocks, stone and mulch, plus mulch before every replant, only to grow crops in winter, which is 15 of the 180 days in a year. Mound Beds now cover the same winter use for less and over a wider area.

Some ideas to give it a real role all year round:

1. More capacity
- Larger interior per building.
- Bigger variants, or a way to expand an existing Greenhouse. The cost per tile of growing space should go down as size goes up, otherwise a bigger Greenhouse would be even less worth building than the current one.

2. Faster growth
- Crops inside grow faster than outdoor fields, in any season.

3. Better quality
- A quality bonus for crops grown inside, or a quality cap tied to the Greenhouse's own quality (like other buildings and tools).

4. Quality of life
- Allow Trellises inside (the 2022 note said this would be fixed later).
- Make mulch last several plantings instead of one, or let it be refilled like Mound Beds since 2026-06-15.

The current cost would be fine if the Greenhouse paid it back. With any of these, it would become a real farming investment instead of a winter-only building that Mound Beds already replace.