Implement Phase 2: Next.js + React Flow frontend MVP

- Scaffold Next.js 15 app with TypeScript, Tailwind, App Router
- Install @xyflow/react, Zustand, Lucide icons, nanoid
- Define council types (AgentNodeData, CouncilBlueprint, WSMessage, etc.)
- Implement Zustand store for canvas and run state
- Build custom AgentNode component (label, system prompt, model badge, tool chips, active pulse)
- Build ConditionalEdge component (dashed indigo line with condition label)
- Build NodeSidebar (drag-and-drop + click to add agents)
- Build NodeSettingsPanel (name, system prompt, model selector, tool toggles)
- Build ArchitectCanvas (React Flow canvas with drop zone, minimap, controls)
- Build blueprint parser (React Flow JSON ↔ CouncilBlueprint JSON)
- Build API client for FastAPI backend (CRUD + run endpoints)
- Build useCouncilWebSocket hook for live agent status via WebSocket
- Build Tab A: Rat-Architekt (canvas builder with save/export toolbar)
- Build Tab B: Konferenzzimmer (execution view with live diagram + result panel)
- Add NavTabs navigation with CouncilOS branding
- All TypeScript checks passing

https://claude.ai/code/session_01EkbecUVn7esdxLCXxVVRDX

frontend/app/components/NavTabs.tsx

@@ -0,0 +1,38 @@
+"use client";
+
+import Link from "next/link";
+import { usePathname } from "next/navigation";
+import { Network, MessagesSquare } from "lucide-react";
+
+const TABS = [
+  { href: "/rat-architekt", label: "Rat-Architekt", icon: Network },
+  { href: "/konferenzzimmer", label: "Konferenzzimmer", icon: MessagesSquare },
+];
+
+export function NavTabs() {
+  const pathname = usePathname();
+
+  return (
+    <nav className="flex items-center gap-1 px-4 py-2 bg-white border-b border-slate-200 flex-shrink-0">
+      <span className="font-bold text-indigo-700 text-sm mr-4">CouncilOS</span>
+      {TABS.map(({ href, label, icon: Icon }) => {
+        const active = pathname.startsWith(href);
+        return (
+          <Link
+            key={href}
+            href={href}
+            className={[
+              "flex items-center gap-1.5 px-3 py-1.5 rounded-lg text-sm font-medium transition-colors",
+              active
+                ? "bg-indigo-50 text-indigo-700"
+                : "text-slate-500 hover:text-slate-700 hover:bg-slate-50",
+            ].join(" ")}
+          >
+            <Icon size={14} />
+            {label}
+          </Link>
+        );
+      })}
+    </nav>
+  );
+}