GroupLink / WelcomeMessage: use SectionDividerSpaced between adjacent cards

Three places had adjacent SectionView cards with no spacer (GroupLinkView QR + actions, WelcomeMessageView non-owner preview + copy), or used a one-off Spacer(8.dp) instead of the conventional helper (owner mode-button card). Replace with SectionDividerSpaced() so all between-card gaps live behind one helper.

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/chat/group/GroupLinkView.kt

@@ -1,6 +1,7 @@
 package chat.simplex.common.views.chat.group
 
 import SectionBottomSpacer
+import SectionDividerSpaced
 import SectionItemView
 import SectionView
 import SectionViewWithButton
@@ -234,6 +235,7 @@ fun GroupLinkLayout(
             } else null) {
           SimpleXCreatedLinkQRCode(groupLink.connLinkContact, short = showShortLink.value)
         }
+        SectionDividerSpaced()
         SectionView {
           if (!isChannel && groupLink.shouldBeUpgraded) {
             SettingsActionItem(

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/chat/group/WelcomeMessageView.kt

@@ -117,7 +117,7 @@ private fun GroupWelcomeLayout(
         color = if (welcomeTextFitsLimit(wt)) MaterialTheme.colors.secondary else Color.Red
       )
 
-      Spacer(Modifier.size(8.dp))
+      SectionDividerSpaced()
 
       SectionView {
         ChangeModeButton(
@@ -142,6 +142,7 @@ private fun GroupWelcomeLayout(
       SectionView(contentPadding = PaddingValues(vertical = DEFAULT_PADDING_HALF)) {
         TextPreview(wt.value, linkMode)
       }
+      SectionDividerSpaced()
       SectionView {
         CopyTextButton { clipboard.setText(AnnotatedString(wt.value)) }
       }