fix(#338): Gate mock data behind NODE_ENV check

- Create ComingSoon component for production placeholders
- Federation connections page shows Coming Soon in production
- Workspaces settings page shows Coming Soon in production
- Teams page shows Coming Soon in production
- Add comprehensive tests for environment-based rendering

Refs #338

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/src/app/(authenticated)/settings/workspaces/page.tsx

@@ -4,10 +4,14 @@ import type { ReactElement } from "react";
 
 import { useState } from "react";
 import { WorkspaceCard } from "@/components/workspace/WorkspaceCard";
+import { ComingSoon } from "@/components/ui/ComingSoon";
 import { WorkspaceMemberRole } from "@mosaic/shared";
 import Link from "next/link";
 
-// Mock data - TODO: Replace with real API calls
+// Check if we're in development mode
+const isDevelopment = process.env.NODE_ENV === "development";
+
+// Mock data - TODO: Replace with real API calls (development only)
 const mockWorkspaces = [
   {
     id: "ws-1",
@@ -32,7 +36,11 @@ const mockMemberships = [
   { workspaceId: "ws-2", role: WorkspaceMemberRole.MEMBER, memberCount: 5 },
 ];
 
-export default function WorkspacesPage(): ReactElement {
+/**
+ * Workspaces Page Content - Development Only
+ * Shows mock workspace data for development purposes
+ */
+function WorkspacesPageContent(): ReactElement {
   const [isCreating, setIsCreating] = useState(false);
   const [newWorkspaceName, setNewWorkspaceName] = useState("");
 
@@ -140,3 +148,26 @@ export default function WorkspacesPage(): ReactElement {
     </main>
   );
 }
+
+/**
+ * Workspaces Page Entry Point
+ * Shows development content or Coming Soon based on environment
+ */
+export default function WorkspacesPage(): ReactElement {
+  // In production, show Coming Soon placeholder
+  if (!isDevelopment) {
+    return (
+      <ComingSoon
+        feature="Workspace Management"
+        description="Create and manage workspaces to organize your projects and collaborate with your team. This feature is currently under development."
+      >
+        <Link href="/settings" className="text-sm text-blue-600 hover:text-blue-700">
+          Back to Settings
+        </Link>
+      </ComingSoon>
+    );
+  }
+
+  // In development, show the full page with mock data
+  return <WorkspacesPageContent />;
+}