refactor: remove persister abstraction layer

Inline persistence logic directly into game stores and handlers:
- game/persist.go: DB mapping methods on GameStore and GameInstance
- snake/persist.go: DB mapping methods on SnakeStore and SnakeGameInstance
- Chat persistence inlined into c4game handlers
- Delete db/persister.go (GamePersister, SnakePersister, ChatPersister)
- Stores now take *repository.Queries directly instead of Persister interface

features/c4game/routes.go

@@ -4,7 +4,7 @@ import (
 	"github.com/alexedwards/scs/v2"
 	"github.com/go-chi/chi/v5"
 	"github.com/nats-io/nats.go"
-	"github.com/ryanhamamura/c4/db"
+	"github.com/ryanhamamura/c4/db/repository"
 	"github.com/ryanhamamura/c4/game"
 )
 
@@ -13,14 +13,14 @@ func SetupRoutes(
 	store *game.GameStore,
 	nc *nats.Conn,
 	sessions *scs.SessionManager,
-	chatPersister *db.ChatPersister,
+	queries *repository.Queries,
 ) error {
-	router.Get("/game/{game_id}", HandleGamePage(store, sessions, chatPersister))
-	router.Get("/game/{game_id}/events", HandleGameEvents(store, nc, sessions, chatPersister))
+	router.Get("/game/{game_id}", HandleGamePage(store, sessions, queries))
+	router.Get("/game/{game_id}/events", HandleGameEvents(store, nc, sessions, queries))
 
 	router.Route("/api/game/{game_id}", func(r chi.Router) {
 		r.Post("/drop", HandleDropPiece(store, sessions))
-		r.Post("/chat", HandleSendChat(store, nc, sessions, chatPersister))
+		r.Post("/chat", HandleSendChat(store, nc, sessions, queries))
 		r.Post("/join", HandleSetNickname(store, sessions))
 		r.Post("/rematch", HandleRematch(store, sessions))
 	})