fix(lint): resolve all errcheck violations in ingestion module

ingestion/internal/watcher/watcher.go

@@ -158,15 +158,15 @@ func copyFile(src, dst string) error {
 	if err != nil {
 		return fmt.Errorf("open src: %w", err)
 	}
-	defer in.Close()
+	defer in.Close() //nolint:errcheck
 
 	out, err := os.Create(dst)
 	if err != nil {
 		return fmt.Errorf("create dst: %w", err)
 	}
-	defer out.Close()
 
 	if _, err := io.Copy(out, in); err != nil {
+		out.Close() //nolint:errcheck
 		return fmt.Errorf("copy: %w", err)
 	}
 	return out.Close()
@@ -201,10 +201,10 @@ func appendWatcherLog(brainDir, filename string, runErr error, date string) erro
 	if err != nil {
 		return fmt.Errorf("open log: %w", err)
 	}
-	defer f.Close()
 
 	if _, err = f.WriteString(entry); err != nil {
+		f.Close() //nolint:errcheck
 		return fmt.Errorf("write log: %w", err)
 	}
-	return nil
+	return f.Close()
 }