Show "Favorites" label below logo when viewing favorites timeline

Adds a visual indicator under the Damus logo when the favorites
timeline is active. Uses fixed height with opacity to prevent
layout bouncing when switching timelines.

damus/Features/Timeline/Views/PostingTimelineView.swift

@@ -95,10 +95,18 @@ struct PostingTimelineView: View {
                 }
                 .frame(maxWidth: .infinity, alignment: .trailing)
                 .overlay {
+                    VStack(spacing: 2) {
                         Image("damus-home")
                             .resizable()
-                        .frame(width:30,height:30)
+                            .frame(width: 30, height: 30)
                             .shadow(color: DamusColors.purple, radius: 2)
+                        if damus_state.settings.enable_favourites_feature {
+                            Text(timeline_source == .favorites ? timeline_source.description : " ")
+                                .font(.caption2)
+                                .foregroundColor(.secondary)
+                                .opacity(timeline_source == .favorites ? 1 : 0)
+                        }
+                    }
                     .opacity(isSideBarOpened ? 0 : 1)
                     .animation(isSideBarOpened ? .none : .default, value: isSideBarOpened)
                     .onTapGesture {