feat(settings): mark Workspace category Coming Soon in the sidebar

Shows a small tertiary-styled 'Coming Soon' next to the category header
whenever every section under it is still !isImplemented — not hardcoded
to Workspace specifically, so it stops on its own once real Workspace
sections start landing instead of needing a manual follow-up removal.

Outpost/Features/Account/SettingsSidebarList.swift

@@ -51,7 +51,18 @@ struct SettingsSidebarList: View {
                         }
                     } header: {
                         if let title = category.title {
-                            Text(title)
+                            HStack(spacing: 6) {
+                                Text(title)
+                                // Not hardcoded to `.workspace` specifically —
+                                // stays correct on its own as sections get
+                                // built, only shows while every section in
+                                // the category is still `!isImplemented`.
+                                if sections.allSatisfy({ !$0.isImplemented }) {
+                                    Text("Coming Soon")
+                                        .font(.caption2.weight(.medium))
+                                        .foregroundStyle(.tertiary)
+                                }
+                            }
                         }
                     }
                 }