feat: enhance logging and message encryption features

- Introduced new logging services: operation logs, login logs, and data change logs.
- Added support for message content encryption in the Message model, including methods for encrypting and decrypting message segments.
- Updated router to include admin log handling and integrated log service for access logging.
- Modified configuration to support encryption settings.

internal/config/encryption.go

@@ -0,0 +1,14 @@
+package config
+
+// EncryptionConfig 消息加密配置
+type EncryptionConfig struct {
+	// Enabled 是否启用消息加密
+	Enabled bool `mapstructure:"enabled"`
+
+	// Key 加密密钥（32字节，AES-256）
+	// 生产环境应通过环境变量 APP_ENCRYPTION_KEY 设置
+	Key string `mapstructure:"key"`
+
+	// KeyVersion 密钥版本，用于密钥轮换
+	KeyVersion int `mapstructure:"key_version"`
+}