Write and run a one-time script to download boss battle trainer sprites from Bulbapedia's archives. For totem pokemon, link to existing pokemon sprites instead.
## Current State
- 10 game directories have sprites (122 files total): red, yellow, gold, crystal, ruby, emerald, firered, diamond, heartgold, omega-ruby
- 11 game directories are completely missing: black, black-2, platinum, x, sun, ultra-sun, lets-go-pikachu, sword, brilliant-diamond, legends-arceus, scarlet
- 11 boss entries have null sprite_url (firered Elite Four + heartgold Elite Four/Red)
## Checklist
- [x] Write download script with Bulbapedia image URL patterns
- [x] Download sprites for all missing games
- [x] Fill in null sprite_url entries for firered/heartgold
- [x] Handle totem pokemon by linking to existing pokemon sprites
- [x] Handle special cases (multi-boss entries, Legends Arceus nobles)
- [x] Update seed JSON files with correct local paths