feat: move some service declarations to core

internal/account/service.go

@@ -7,7 +7,6 @@ import (
 	"log/slog"
 	"spend-sparrow/internal/auth_types"
 	"spend-sparrow/internal/core"
-	"spend-sparrow/internal/service"
 
 	"github.com/google/uuid"
 	"github.com/jmoiron/sqlx"
@@ -45,7 +44,7 @@ func (s ServiceImpl) Add(ctx context.Context, user *auth_types.User, name string
 		return nil, core.ErrInternal
 	}
 
-	err = service.ValidateString(name, "name")
+	err = core.ValidateString(name, "name")
 	if err != nil {
 		return nil, err
 	}
@@ -81,7 +80,7 @@ func (s ServiceImpl) UpdateName(ctx context.Context, user *auth_types.User, id s
 	if user == nil {
 		return nil, core.ErrUnauthorized
 	}
-	err := service.ValidateString(name, "name")
+	err := core.ValidateString(name, "name")
 	if err != nil {
 		return nil, err
 	}