feat(db): 添加对达梦数据库的支持

- 在应用程序中新增对达梦数据库（DM）的配置和连接支持
- 实现 SetDmDB 函数以配置达梦数据库连接
- 更新数据库操作逻辑，支持达梦特有的 SQL 语法和功能
- 在相关文件中添加达梦数据库的处理逻辑，包括表创建、数据插入和查询
- 更新 go.mod 和 go.sum 文件以引入达梦数据库驱动
- 增强文档，详细说明达梦数据库的配置和使用方法

db/dialect.go

@@ -206,6 +206,100 @@ func (d *PostgreSQLDialect) UpsertSQL(table string, columns []string, uniqueKeys
 		strings.Join(updateParts, ", "))
 }
 
+// DMDialect 达梦数据库方言实现
+type DMDialect struct{}
+
+func (d *DMDialect) GetName() string {
+	return "dm"
+}
+
+func (d *DMDialect) Quote(name string) string {
+	if strings.Contains(name, ".") || strings.Contains(name, " ") {
+		return name
+	}
+	return "\"" + name + "\""
+}
+
+func (d *DMDialect) QuoteIdentifier(name string) string {
+	name = strings.Trim(name, "`\"")
+	return "\"" + name + "\""
+}
+
+func (d *DMDialect) QuoteChar() string {
+	return "\""
+}
+
+func (d *DMDialect) Placeholder(index int) string {
+	return "?"
+}
+
+func (d *DMDialect) Placeholders(count int, startIndex int) string {
+	if count <= 0 {
+		return ""
+	}
+	placeholders := make([]string, count)
+	for i := 0; i < count; i++ {
+		placeholders[i] = "?"
+	}
+	return strings.Join(placeholders, ",")
+}
+
+func (d *DMDialect) SupportsLastInsertId() bool {
+	return true // DM Go 驱动原生支持 IDENTITY 列的 LastInsertId
+}
+
+func (d *DMDialect) ReturningClause(column string) string {
+	return " RETURNING " + d.Quote(column)
+}
+
+func (d *DMDialect) UpsertSQL(table string, columns []string, uniqueKeys []string, updateColumns []string) string {
+	// MERGE INTO table USING (SELECT ? AS col1, ? AS col2) src
+	// ON (table.uk = src.uk) WHEN MATCHED THEN UPDATE SET col1 = src.col1
+	// WHEN NOT MATCHED THEN INSERT (col1, col2) VALUES (src.col1, src.col2)
+	quotedTable := d.Quote(table)
+
+	srcParts := make([]string, len(columns))
+	for i, col := range columns {
+		if strings.HasSuffix(col, "[#]") {
+			srcParts[i] = col
+		} else {
+			srcParts[i] = "? AS " + d.Quote(col)
+		}
+	}
+
+	onParts := make([]string, len(uniqueKeys))
+	for i, key := range uniqueKeys {
+		qk := d.Quote(key)
+		onParts[i] = quotedTable + "." + qk + " = src." + qk
+	}
+
+	updateParts := make([]string, len(updateColumns))
+	for i, col := range updateColumns {
+		if strings.HasSuffix(col, "[#]") {
+			updateParts[i] = col
+		} else {
+			qc := d.Quote(col)
+			updateParts[i] = qc + " = src." + qc
+		}
+	}
+
+	insertCols := make([]string, len(columns))
+	insertVals := make([]string, len(columns))
+	for i, col := range columns {
+		qc := d.Quote(col)
+		insertCols[i] = qc
+		insertVals[i] = "src." + qc
+	}
+
+	return fmt.Sprintf("MERGE INTO %s USING (SELECT %s) src ON (%s) WHEN MATCHED THEN UPDATE SET %s WHEN NOT MATCHED THEN INSERT (%s) VALUES (%s)",
+		quotedTable,
+		strings.Join(srcParts, ", "),
+		strings.Join(onParts, " AND "),
+		strings.Join(updateParts, ", "),
+		strings.Join(insertCols, ", "),
+		strings.Join(insertVals, ", "))
+}
+
 // SQLiteDialect SQLite 方言实现
 type SQLiteDialect struct{}