refactor: rename game package to connect4, drop Game prefix from types

Rename game/ -> connect4/ to avoid c4/game stutter. Drop redundant
Game prefix from exported types (GameStore -> Store, GameInstance ->
Instance, GameStatus -> Status). Rename NATS subjects from game.{id}
to connect4.{id}. URL routes unchanged.

features/c4game/routes.go

@@ -6,13 +6,13 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/nats-io/nats.go"
 
+	"github.com/ryanhamamura/c4/connect4"
 	"github.com/ryanhamamura/c4/db/repository"
-	"github.com/ryanhamamura/c4/game"
 )
 
 func SetupRoutes(
 	router chi.Router,
-	store *game.GameStore,
+	store *connect4.Store,
 	nc *nats.Conn,
 	sessions *scs.SessionManager,
 	queries *repository.Queries,