feat: 新增会话ID伪装功能，优化日志系统

- 新增 session_id_masking_enabled 配置，启用后将在15分钟内固定
  metadata.user_id 中的 session ID
- TLS fingerprint 模块日志从自定义 debugLog 迁移到 slog
- main.go 添加 slog 初始化，根据 gin mode 设置日志级别
- 前端创建/编辑账号模态框添加会话ID伪装开关
- 多语言支持（中英文）

backend/internal/pkg/tlsfingerprint/registry.go

@@ -2,6 +2,7 @@
 package tlsfingerprint
 
 import (
+	"log/slog"
 	"sort"
 	"sync"
 
@@ -40,7 +41,7 @@ func NewRegistryFromConfig(cfg *config.TLSFingerprintConfig) *Registry {
 	r := NewRegistry()
 
 	if cfg == nil || !cfg.Enabled {
-		debugLog("[TLS Registry] TLS fingerprint disabled or no config, using default profile only")
+		slog.Debug("tls_registry_disabled", "reason", "disabled or no config")
 		return r
 	}
 
@@ -56,10 +57,10 @@ func NewRegistryFromConfig(cfg *config.TLSFingerprintConfig) *Registry {
 
 		// If the profile has empty values, they will use defaults in dialer
 		r.RegisterProfile(name, profile)
-		debugLog("[TLS Registry] Loaded custom profile: %s (%s)", name, profileCfg.Name)
+		slog.Debug("tls_registry_loaded_profile", "key", name, "name", profileCfg.Name)
 	}
 
-	debugLog("[TLS Registry] Initialized with %d profiles: %v", len(r.profileNames), r.profileNames)
+	slog.Debug("tls_registry_initialized", "profile_count", len(r.profileNames), "profiles", r.profileNames)
 	return r
 }