工具
计算器与 /api/v1/tools/:id JSON 共用，便于后续 Flutter。
- Troop training Infantry / Cavalry / Archer T1–T11 — bread, wood, stone, iron & time.
- Kingdom age timeline Fog, hero gens, pets, Truegold, War Academy, KvK eligibility by day.
计算器与 /api/v1/tools/:id JSON 共用，便于后续 Flutter。