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.

main.go

@@ -12,9 +12,9 @@ import (
 	"time"
 
 	"github.com/ryanhamamura/c4/config"
+	"github.com/ryanhamamura/c4/connect4"
 	"github.com/ryanhamamura/c4/db"
 	"github.com/ryanhamamura/c4/db/repository"
-	"github.com/ryanhamamura/c4/game"
 	"github.com/ryanhamamura/c4/logging"
 	appnats "github.com/ryanhamamura/c4/nats"
 	"github.com/ryanhamamura/c4/router"
@@ -71,9 +71,9 @@ func run(ctx context.Context) error {
 	defer cleanupNATS()
 
 	// Game stores
-	store := game.NewGameStore(queries)
+	store := connect4.NewStore(queries)
 	store.SetNotifyFunc(func(gameID string) {
-		nc.Publish("game."+gameID, nil) //nolint:errcheck // best-effort notification
+		nc.Publish("connect4."+gameID, nil) //nolint:errcheck // best-effort notification
 	})
 
 	snakeStore := snake.NewSnakeStore(queries)