refactor(api): inject BookPersistence/UserPersistence at HTTP layer

- NewRouter accepts *gorm.DB and constructs GORM-backed stores internally.
- NewBookRepository and NewUserRepository take persistence interfaces,
  matching service boundaries and allowing gomock at the store API.
- readyz postgres probe uses *gorm.DB directly (no type assertion).
- Fail fast in main when NewDatabase returns nil.
- Extend probe tests with an in-memory SQLite ping.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: leo-aa88

cmd/server/main.go

@@ -74,7 +74,9 @@ func main() {
 		log.Fatalf("redis: %v", err)
 	}
 	db := database.NewDatabase()
-	dbWrapper := &database.GormDatabase{DB: db}
+	if db == nil {
+		log.Fatal("database: could not connect or migrate (see logs above)")
+	}
 	mongo := database.SetupMongoDB()
 	logger, err := zap.NewProduction()
 	if err != nil {
@@ -90,7 +92,7 @@ func main() {
 	// Gin's init already applied os.Getenv("GIN_MODE"); do not override here.
 	// Use GIN_MODE=release in production so Security/XSS middleware run (pkg/api/router.go).
 
-	r := api.NewRouter(logger, mongo, dbWrapper, redisClient)
+	r := api.NewRouter(logger, mongo, db, redisClient)
 
 	const (
 		serverAddr          = ":8001"

pkg/api/books.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 
 	"golang-rest-api-template/pkg/cache"
-	"golang-rest-api-template/pkg/database"
 	"golang-rest-api-template/pkg/models"
 	"golang-rest-api-template/pkg/repository"
 	"golang-rest-api-template/pkg/service"
@@ -35,8 +34,7 @@ type bookRepository struct {
 }
 
 // NewBookRepository wires persistence and cache into book HTTP handlers.
-func NewBookRepository(db database.Database, redisClient cache.Cache) *bookRepository {
-	store := repository.NewGormBookStore(db)
+func NewBookRepository(store repository.BookPersistence, redisClient cache.Cache) *bookRepository {
 	return &bookRepository{svc: service.NewBookService(store, redisClient)}
 }