refactor: use dialect-neutral Jet type aliases

Replace mysql/postgres intersection interfaces with mysql type aliases
per go-jet/jet#555 and generalize Apply/Expr signatures.

Co-authored-by: Cursor <cursoragent@cursor.com>

apply.go

@@ -3,7 +3,6 @@ package dbx
 import (
 	"reflect"
 
-	"github.com/go-jet/jet/v2/mysql"
 	"golang.org/x/exp/constraints"
 )
 
@@ -19,8 +18,8 @@ type ApplyInterface[T any] interface {
 func ApplyPtr[T constraints.Float | constraints.Integer | string | bool](
 	existing *T,
 	newVal *T,
-	updatedColumns *mysql.ColumnList,
-	targetColumn mysql.Column,
+	updatedColumns *ColumnList,
+	targetColumn Column,
 ) *T {
 	if newVal == nil {
 		return existing
@@ -46,8 +45,8 @@ func ApplyComplexPtr[
 ](
 	existing *Existing,
 	newVal *New,
-	updatedColumns *mysql.ColumnList,
-	targetColumn mysql.Column,
+	updatedColumns *ColumnList,
+	targetColumn Column,
 ) *Existing {
 	if newVal == nil {
 		return existing
@@ -73,8 +72,8 @@ func ApplyComplexPtr[
 func ApplyInterfacePtr[T ApplyInterface[T]](
 	existing *T,
 	newVal *T,
-	updatedColumns *mysql.ColumnList,
-	targetColumn mysql.Column,
+	updatedColumns *ColumnList,
+	targetColumn Column,
 ) *T {
 	if newVal == nil {
 		return existing
@@ -98,8 +97,8 @@ func ApplyInterfacePtr[T ApplyInterface[T]](
 func ApplyVal[T constraints.Float | constraints.Integer | string | bool](
 	existing T,
 	newVal *T,
-	updatedColumns *mysql.ColumnList,
-	targetColumn mysql.Column,
+	updatedColumns *ColumnList,
+	targetColumn Column,
 ) T {
 	if newVal == nil {
 		return existing