refactor: Flatten directory structure

Move project files from uzdb/ subdirectory to root directory for cleaner project structure.

Changes:
- Move frontend/ to root
- Move internal/ to root
- Move build/ to root
- Move all config files (go.mod, wails.json, etc.) to root
- Remove redundant uzdb/ subdirectory nesting

Project structure is now:
├── frontend/        # React application
├── internal/        # Go backend
├── build/           # Wails build assets
├── doc/             # Design documentation
├── main.go          # Entry point
└── ...

🤖 Generated with Qoder

internal/services/encryption.go

@@ -0,0 +1,199 @@
+package services
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"os"
+	"sync"
+
+	"go.uber.org/zap"
+
+	"uzdb/internal/config"
+	"uzdb/internal/models"
+	"uzdb/internal/utils"
+)
+
+// EncryptionService handles encryption and decryption of sensitive data
+type EncryptionService struct {
+	key     []byte
+	cipher  cipher.Block
+	gcm     cipher.AEAD
+	mu      sync.RWMutex
+}
+
+var (
+	encryptionInstance *EncryptionService
+	encryptionOnce     sync.Once
+)
+
+// GetEncryptionService returns the singleton encryption service instance
+func GetEncryptionService() *EncryptionService {
+	return encryptionInstance
+}
+
+// InitEncryptionService initializes the encryption service
+func InitEncryptionService(cfg *config.EncryptionConfig) (*EncryptionService, error) {
+	var err error
+	encryptionOnce.Do(func() {
+		encryptionInstance = &EncryptionService{}
+		err = encryptionInstance.init(cfg)
+	})
+	return encryptionInstance, err
+}
+
+// init initializes the encryption service with a key
+func (s *EncryptionService) init(cfg *config.EncryptionConfig) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// Try to load existing key or generate new one
+	key, err := s.loadOrGenerateKey(cfg)
+	if err != nil {
+		return fmt.Errorf("failed to load/generate key: %w", err)
+	}
+
+	s.key = key
+
+	// Create AES cipher
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return fmt.Errorf("failed to create cipher: %w", err)
+	}
+	s.cipher = block
+
+	// Create GCM mode
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return fmt.Errorf("failed to create GCM: %w", err)
+	}
+	s.gcm = gcm
+
+	config.GetLogger().Info("encryption service initialized")
+	return nil
+}
+
+// loadOrGenerateKey loads existing key or generates a new one
+func (s *EncryptionService) loadOrGenerateKey(cfg *config.EncryptionConfig) ([]byte, error) {
+	// Use provided key if available
+	if cfg.Key != "" {
+		key := []byte(cfg.Key)
+		// Ensure key is correct length (32 bytes for AES-256)
+		if len(key) < 32 {
+			// Pad key
+			padded := make([]byte, 32)
+			copy(padded, key)
+			key = padded
+		} else if len(key) > 32 {
+			key = key[:32]
+		}
+		return key, nil
+	}
+
+	// Try to load from file
+	if cfg.KeyFile != "" {
+		if data, err := os.ReadFile(cfg.KeyFile); err == nil {
+			key := []byte(data)
+			if len(key) >= 32 {
+				return key[:32], nil
+			}
+		}
+	}
+
+	// Generate new key
+	key := make([]byte, 32) // AES-256
+	if _, err := io.ReadFull(rand.Reader, key); err != nil {
+		return nil, fmt.Errorf("failed to generate key: %w", err)
+	}
+
+	// Save key to file if path provided
+	if cfg.KeyFile != "" {
+		if err := os.WriteFile(cfg.KeyFile, key, 0600); err != nil {
+			config.GetLogger().Warn("failed to save encryption key", zap.Error(err))
+		} else {
+			config.GetLogger().Info("encryption key generated and saved",
+				zap.String("path", cfg.KeyFile))
+		}
+	}
+
+	return key, nil
+}
+
+// Encrypt encrypts plaintext using AES-GCM
+func (s *EncryptionService) Encrypt(plaintext string) (string, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	if s.gcm == nil {
+		return "", models.ErrEncryptionFailed
+	}
+
+	// Generate nonce
+	nonce := make([]byte, s.gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return "", fmt.Errorf("failed to generate nonce: %w", err)
+	}
+
+	// Encrypt
+	ciphertext := s.gcm.Seal(nonce, nonce, []byte(plaintext), nil)
+
+	// Encode to base64
+	return base64.StdEncoding.EncodeToString(ciphertext), nil
+}
+
+// Decrypt decrypts ciphertext using AES-GCM
+func (s *EncryptionService) Decrypt(ciphertext string) (string, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	if s.gcm == nil {
+		return "", models.ErrEncryptionFailed
+	}
+
+	// Decode from base64
+	data, err := base64.StdEncoding.DecodeString(ciphertext)
+	if err != nil {
+		return "", fmt.Errorf("failed to decode ciphertext: %w", err)
+	}
+
+	// Verify nonce size
+	nonceSize := s.gcm.NonceSize()
+	if len(data) < nonceSize {
+		return "", models.ErrEncryptionFailed
+	}
+
+	// Extract nonce and ciphertext
+	nonce, ciphertextBytes := data[:nonceSize], data[nonceSize:]
+
+	// Decrypt
+	plaintext, err := s.gcm.Open(nil, nonce, ciphertextBytes, nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to decrypt: %w", err)
+	}
+
+	return string(plaintext), nil
+}
+
+// EncryptPassword encrypts a password for storage
+func (s *EncryptionService) EncryptPassword(password string) (string, error) {
+	if password == "" {
+		return "", nil
+	}
+	return s.Encrypt(password)
+}
+
+// DecryptPassword decrypts a stored password
+func (s *EncryptionService) DecryptPassword(encryptedPassword string) (string, error) {
+	if encryptedPassword == "" {
+		return "", nil
+	}
+	return s.Decrypt(encryptedPassword)
+}
+
+// MaskPasswordForLogging masks password for safe logging
+func (s *EncryptionService) MaskPasswordForLogging(password string) string {
+	return utils.MaskPassword(password)
+}