Add stability hardening and self-heal recovery

audit/internal/app/atomic_write.go

@@ -0,0 +1,48 @@
+package app
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+func atomicWriteFile(path string, data []byte, perm os.FileMode) error {
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+		return fmt.Errorf("mkdir %s: %w", filepath.Dir(path), err)
+	}
+
+	tmpPath := path + ".tmp"
+	f, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, perm)
+	if err != nil {
+		return fmt.Errorf("open temp %s: %w", tmpPath, err)
+	}
+
+	success := false
+	defer func() {
+		_ = f.Close()
+		if !success {
+			_ = os.Remove(tmpPath)
+		}
+	}()
+
+	if _, err := f.Write(data); err != nil {
+		return fmt.Errorf("write temp %s: %w", tmpPath, err)
+	}
+	if err := f.Sync(); err != nil {
+		return fmt.Errorf("sync temp %s: %w", tmpPath, err)
+	}
+	if err := f.Close(); err != nil {
+		return fmt.Errorf("close temp %s: %w", tmpPath, err)
+	}
+	if err := os.Rename(tmpPath, path); err != nil {
+		return fmt.Errorf("rename %s -> %s: %w", tmpPath, path, err)
+	}
+
+	if dir, err := os.Open(filepath.Dir(path)); err == nil {
+		_ = dir.Sync()
+		_ = dir.Close()
+	}
+
+	success = true
+	return nil
+}