feat: 新增 DuckDB 方言支持及 SQLite3 自动注册 IF 函数

- 新增 dialect/duckdb 方言，支持 DuckDB SQL 语法
- 新增 schema/dialect/duckdb DDL 操作支持
- dialect/sqlite3: 注册 sqlite3_with_if 驱动，连接时自动注册 IF() 函数
- engine: MakeConnection 对 sqlite3 自动使用带 IF 支持的驱动
- engine: 新增 DBConfig DuckDB 配置项及相关 Option 函数
- 统一各方言测试引用路径

engine/engine.go

@@ -2,15 +2,11 @@ package engine
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 
-	_ "git.fsdpf.net/go/db/dialect/mysql"
-	_ "git.fsdpf.net/go/db/dialect/postgres"
-	_ "git.fsdpf.net/go/db/dialect/sqlite3"
-	_ "git.fsdpf.net/go/db/dialect/sqlserver"
-
 	"git.fsdpf.net/go/db"
-	"git.fsdpf.net/go/db/internal/errors"
+	sqlite3dialect "git.fsdpf.net/go/db/dialect/sqlite3"
 )
 
 type Engine struct {
@@ -47,16 +43,19 @@ func (e Engine) Connection(name string) *db.Database {
 func (e Engine) MakeConnection(cfg DBConfig) (db *sql.DB) {
 	dsn := cfg.ToDSN()
 
+	driverName := cfg.Driver
 	switch cfg.Driver {
 	case "mysql":
 	case "sqlite3":
+		driverName = sqlite3dialect.DriverWithIF
 	case "sqlserver":
 	case "postgres":
+	case "duckdb":
 	default:
 		panic(fmt.Sprintf("Unsupported driver: %s", cfg.Driver))
 	}
 
-	db, err := sql.Open(cfg.Driver, dsn)
+	db, err := sql.Open(driverName, dsn)
 
 	if err != nil {
 		panic(err)