refactor: extract configuration management to config/config.go

- Move defaultConfig() and loadConfig() functions to config package
- Remove unused yaml import from main.go
- Clean separation of configuration logic
- Update main() to use config.Load()

Reduced main.go from ~3650 to ~3570 lines

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

main.go

@@ -27,8 +27,8 @@ import (
 	"github.com/klauspost/compress/zstd"
 	"github.com/robfig/cron/v3"
 	"github.com/sirupsen/logrus"
-	"gopkg.in/yaml.v3"
 
+	"kvs/config"
 	"kvs/types"
 	"kvs/utils"
 )
@@ -1179,89 +1179,6 @@ func (s *Server) getBackupStatus() types.BackupStatus {
 	return status
 }
 
-// Default configuration
-func defaultConfig() *types.Config {
-	hostname, _ := os.Hostname()
-	return &types.Config{
-		NodeID:               hostname,
-		BindAddress:          "127.0.0.1",
-		Port:                 8080,
-		DataDir:              "./data",
-		SeedNodes:            []string{},
-		ReadOnly:             false,
-		LogLevel:             "info",
-		GossipIntervalMin:    60,  // 1 minute
-		GossipIntervalMax:    120, // 2 minutes
-		SyncInterval:         300, // 5 minutes
-		CatchupInterval:      120, // 2 minutes
-		BootstrapMaxAgeHours: 720, // 30 days
-		ThrottleDelayMs:      100,
-		FetchDelayMs:         50,
-		
-		// Phase 2: Default compression settings
-		CompressionEnabled: true,
-		CompressionLevel:   3, // Balance between performance and compression ratio
-		
-		// Phase 2: Default TTL and size limit settings
-		DefaultTTL:  "0",       // No default TTL
-		MaxJSONSize: 1048576,   // 1MB default max JSON size
-		
-		// Phase 2: Default rate limiting settings
-		RateLimitRequests: 100,  // 100 requests per window
-		RateLimitWindow:   "1m", // 1 minute window
-		
-		// Phase 2: Default tamper-evident logging settings
-		TamperLogActions: []string{"data_write", "user_create", "auth_failure"},
-		
-		// Phase 2: Default backup system settings
-		BackupEnabled:   true,
-		BackupSchedule:  "0 0 * * *", // Daily at midnight
-		BackupPath:      "./backups",
-		BackupRetention: 7, // Keep backups for 7 days
-		
-		// Default feature toggle settings (all enabled by default)
-		AuthEnabled:            true,
-		TamperLoggingEnabled:   true,
-		ClusteringEnabled:      true,
-		RateLimitingEnabled:    true,
-		RevisionHistoryEnabled: true,
-	}
-}
-
-// Load configuration from file or create default
-func loadConfig(configPath string) (*types.Config, error) {
-	config := defaultConfig()
-
-	if _, err := os.Stat(configPath); os.IsNotExist(err) {
-		// Create default config file
-		if err := os.MkdirAll(filepath.Dir(configPath), 0755); err != nil {
-			return nil, fmt.Errorf("failed to create config directory: %v", err)
-		}
-
-		data, err := yaml.Marshal(config)
-		if err != nil {
-			return nil, fmt.Errorf("failed to marshal default config: %v", err)
-		}
-
-		if err := os.WriteFile(configPath, data, 0644); err != nil {
-			return nil, fmt.Errorf("failed to write default config: %v", err)
-		}
-
-		fmt.Printf("Created default configuration at %s\n", configPath)
-		return config, nil
-	}
-
-	data, err := os.ReadFile(configPath)
-	if err != nil {
-		return nil, fmt.Errorf("failed to read config file: %v", err)
-	}
-
-	if err := yaml.Unmarshal(data, config); err != nil {
-		return nil, fmt.Errorf("failed to parse config file: %v", err)
-	}
-
-	return config, nil
-}
 
 // Initialize server
 func NewServer(config *types.Config) (*Server, error) {
@@ -3675,13 +3592,13 @@ func main() {
 		configPath = os.Args[1]
 	}
 
-	config, err := loadConfig(configPath)
+	cfg, err := config.Load(configPath)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to load configuration: %v\n", err)
 		os.Exit(1)
 	}
 
-	server, err := NewServer(config)
+	server, err := NewServer(cfg)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to create server: %v\n", err)
 		os.Exit(1)