feat(misc): default /gacha options to 5 stars with a 3*/4* prefix

Rarity is now a leading prefix such as "4* Pho" or "3* Rice"; options
without one are 5 stars. This replaces the trailing "*5" tag and its
3-star default.

docs/deploy-coolify-selfhosted.md

@@ -89,8 +89,9 @@ reply is immediate.
 segment, so `.../api/gif` becomes `.../api/gacha`. It renders a 7-second
 `640x360` silent MP4 wish animation, posts `Wishing...` while it renders, and
 falls back to a text reply such as `★★★★★ Pizza` on the same failures. Every
-option is equally likely, as with `/random`; a `*4` or `*5` tag only sets the
-rarity shown in the animation and reply. Untagged options are 3★.
+option is equally likely, as with `/random`; the rarity only sets what the
+animation and reply show. Options are 5★ by default; prefix `4*` or `3*` to
+lower one, e.g. `/gacha Pizza, 4* Pho, 3* Rice`.
 
 ## 1. MongoDB Atlas (M0)