perf: optimize XSettings1 startup by removing Before constraint and skipping redundant init

Remove the Before=org.dde.session.Daemon1.service ordering constraint so
XSettings1 and dde-session-daemon can start in parallel. On subsequent
boots where the scale factor is already persisted in DConfig, skip the
expensive RandR monitor enumeration, Plymouth scaling, and Greeter Qt
theme update — saving approximately 100-350ms per login. First boot
behavior is unchanged.

移除对 dde-session-daemon 的 Before 排序约束，使 XSettings1 和 dde-session-daemon
可以并行启动。后续登录时（缩放比已持久化到 DConfig），跳过 RandR 显示器枚举、
Plymouth 缩放通知和 Greeter Qt 主题更新等冗余操作，每次登录节省约 100-350ms。
首次启动行为不变。

Log: perf: optimize XSettings1 startup by removing Before constraint and skipping redundant init
Change-Id: If46f0e440459812e52f579aa9ec02c4d758336a2

Author: yixinshark

src/plugin-qt/xsettings/impl/xsettingsmanager.cpp

@@ -30,8 +30,18 @@ XSettingsManager::XSettingsManager(QObject *parent)
     , m_xcbUtils(XcbUtils::getInstance())
 {
     connect(m_settingDconfig, &DTK_CORE_NAMESPACE::DConfig::valueChanged, this, &XSettingsManager::handleDConfigChangedCb);
-    setScreenScaleFactors(getScreenScaleFactors(), false);
-    adjustScaleFactor(getRecommendedScaleFactor());
+
+    double scale = 0;
+    if (m_settingDconfig->isValid()) {
+        scale = m_settingDconfig->value("scale-factor").toDouble();
+    }
+
+    // scale <= 0 is invalid, use recommended scale factor
+    if (scale <= 0) {
+        setScreenScaleFactors(getScreenScaleFactors(), false);
+        adjustScaleFactor(getRecommendedScaleFactor());
+    }
+
     setSettings(getSettingsInSchema());
 
     updateDPI();

src/plugin-qt/xsettings/misc/org.deepin.dde.XSettings1.service

@@ -7,8 +7,6 @@ CollectMode=inactive-or-failed
 PartOf=dde-session-pre.target
 Before=dde-session-pre.target
 
-Before=org.dde.session.Daemon1.service
-
 [Service]
 Type=dbus
 BusName=org.deepin.dde.XSettings1