Enhance database models with comments and table descriptions

- Added comments to various fields in the database models for better clarity and understanding.
- Implemented TableComment methods for several models to provide descriptive information about their purpose.
- Updated the AutoMigrate function to support setting table comments in the database.
- Improved overall documentation within the code to facilitate future maintenance and development.

internal/database/database.go

@@ -3,6 +3,7 @@ package database
 import (
 	"fmt"
 	"log"
+	"strings"
 	"wx_service/config"
 
 	"gorm.io/driver/mysql"
@@ -37,5 +38,36 @@ func InitDB() error {
 }
 
 func AutoMigrate(models ...interface{}) error {
-	return DB.AutoMigrate(models...)
+	type tableCommenter interface {
+		TableComment() string
+	}
+
+	for _, m := range models {
+		tx := DB
+		comment := ""
+		if tc, ok := m.(tableCommenter); ok {
+			comment = strings.TrimSpace(tc.TableComment())
+			if comment != "" {
+				tx = tx.Set("gorm:table_options", fmt.Sprintf("COMMENT='%s'", escapeSQLComment(comment)))
+			}
+		}
+
+		if err := tx.AutoMigrate(m); err != nil {
+			return err
+		}
+
+		// 尝试为已存在的表补齐 table comment（即使表已创建，也能更新注释）。
+		if comment != "" {
+			stmt := &gorm.Statement{DB: DB}
+			if err := stmt.Parse(m); err == nil && stmt.Schema != nil && stmt.Schema.Table != "" {
+				_ = DB.Exec(fmt.Sprintf("ALTER TABLE `%s` COMMENT = '%s'", stmt.Schema.Table, escapeSQLComment(comment))).Error
+			}
+		}
+	}
+	return nil
+}
+
+func escapeSQLComment(s string) string {
+	// MySQL: 单引号用两个单引号转义
+	return strings.ReplaceAll(s, "'", "''")
 }