Refactor db package logging

internal/db/schema.go

@@ -17,7 +17,8 @@ var migrations embed.FS
 // ApplySchema reads the current database version from PRAGMA user_version
 // and applies any pending migrations in a single transaction. Each migration
 // file runs in order; if any fail the entire transaction rolls back and the
-// version is unchanged.
+// version is unchanged. log must be non-nil; pass
+// slog.New(slog.DiscardHandler) to run without logs.
 //
 // Migration files are named <version>.<description>. The version
 // must be a non-negative integer. On success, PRAGMA user_version is set
@@ -27,7 +28,7 @@ var migrations embed.FS
 // the application code expects a schema that matches the latest migration.
 func (s *SQLite) ApplySchema(ctx context.Context, log *slog.Logger) error {
 	if log == nil {
-		log = slog.Default()
+		return fmt.Errorf("logger is nil")
 	}
 
 	var currentVersion int