Fix black text in drag preview when moving a chat to a folder

.draggable()'s default drag-preview snapshot wasn't inheriting the
app's dark appearance, rendering the conversation name in black on a
transparent background while dragging. Supply an explicit preview
view instead — white text on the accent color pill — so it stays
legible for the duration of the drag, independent of the row's own
(already-correct) rendering before and after the move.

oAI/Views/Main/SidebarView.swift

@@ -230,7 +230,14 @@ struct SidebarView: View {
                     ? Color.oaiAccent.opacity(0.15)
                     : Color.clear
             )
-            .draggable(conversation.id.uuidString)
+            .draggable(conversation.id.uuidString) {
+                Text(conversation.name)
+                    .font(.system(size: 13, weight: .medium))
+                    .foregroundStyle(.white)
+                    .padding(.horizontal, 10)
+                    .padding(.vertical, 6)
+                    .background(Color.oaiAccent, in: RoundedRectangle(cornerRadius: 6))
+            }
             .swipeActions(edge: .trailing, allowsFullSwipe: false) {
                 Button(role: .destructive) {
                     deleteConversation(conversation)

oAI/Views/Screens/ConversationListView.swift

@@ -348,7 +348,14 @@ struct ConversationListView: View {
                 : Color.clear
         )
         .id(conversation.id)
-        .draggable(conversation.id.uuidString)
+        .draggable(conversation.id.uuidString) {
+            Text(conversation.name)
+                .font(.system(size: 13, weight: .medium))
+                .foregroundStyle(.white)
+                .padding(.horizontal, 10)
+                .padding(.vertical, 6)
+                .background(Color.oaiAccent, in: RoundedRectangle(cornerRadius: 6))
+        }
         .swipeActions(edge: .trailing, allowsFullSwipe: false) {
             Button(role: .destructive) {
                 deleteConversation(conversation)