fix: adapt search edit icon size to size mode

1. Root cause: DSearchEditPrivate::init() hardcoded icon size to
   QSize(20, 20) without DSizeMode awareness, causing oversized
   icon in compact mode
2. Fix: use DSizeModeHelper::element() for adaptive sizing and
   connect sizeModeChanged signal for dynamic updates
3. Impact: all DSearchEdit instances now adapt icon size to
   compact/normal mode

Log: Fix search edit icon not adapting to compact mode

Influence:
1. Test DSearchEdit icon display in normal mode
2. Test DSearchEdit icon display in compact mode
3. Verify icon updates when switching size modes at runtime

fix: 搜索框图标尺寸适配紧凑模式

1. 根因：DSearchEditPrivate::init() 硬编码图标尺寸为
   QSize(20, 20)，不随 DSizeMode 自适应
2. 方案：使用 DSizeModeHelper::element() 实现自适应尺寸，
   并监听 sizeModeChanged 信号动态更新
3. 影响：所有 DSearchEdit 实例的图标尺寸将随紧凑/正常模式自适应

Log: 修复搜索框图标在紧凑模式下过大的问题

Influence:
1. 测试正常模式下搜索框图标显示
2. 测试紧凑模式下搜索框图标显示
3. 验证运行时切换尺寸模式时图标是否动态更新

PMS: BUG-224407

Author: GongHeng2017

src/widgets/dsearchedit.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2015 - 2022 UnionTech Software Technology Co., Ltd.
+// SPDX-FileCopyrightText: 2015 - 2026 UnionTech Software Technology Co., Ltd.
 //
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
@@ -7,6 +7,7 @@
 #include "dstyle.h"
 #include "private/dsearchedit_p.h"
 #include "diconbutton.h"
+#include "dsizemode.h"
 
 #include <DSysInfo>
 #include <DGuiApplicationHelper>
@@ -300,7 +301,7 @@ void DSearchEditPrivate::init()
         iconbtn->setFocusPolicy(Qt::NoFocus);
         iconbtn->setAttribute(Qt::WA_TransparentForMouseEvents);
         iconbtn->setAccessibleName("DSearchEditIconButton");
-        iconbtn->setIconSize(QSize(20, 20));
+        iconbtn->setIconSize(DSizeModeHelper::element(QSize(16, 16), QSize(20, 20)));
         return iconbtn;
     };
 
@@ -315,6 +316,14 @@ void DSearchEditPrivate::init()
     q->lineEdit()->addAction(action, QLineEdit::LeadingPosition);
     action->defaultWidget()->setVisible(false);
 
+    auto updateIconSize = [iconbtn, iconAction]() {
+        QSize iconSize = DSizeModeHelper::element(QSize(16, 16), QSize(20, 20));
+        iconbtn->setIconSize(iconSize);
+        iconAction->setIconSize(iconSize);
+    };
+    updateIconSize();
+    QObject::connect(DGuiApplicationHelper::instance(), &DGuiApplicationHelper::sizeModeChanged, q, updateIconSize);
+
     DPalette pe;
     QStyleOption opt;
     QColor color = DStyleHelper(q->style()).getColor(&opt, pe, DPalette::TextTips);