feat: Dashboard Backend Proxy – OpenClaw Gateway Integration

- DashboardController: /api/dashboard/status, agents, operations, chat/send, chat/messages, queue
- OpenClawGatewayClient: typed HttpClient mit Gateway tools/invoke
- Dashboard DTOs: DashboardAgentInfo, ChatRequest, ChatResponse, FeedEntry, QueueItem
- Gateway auth: Bearer-Password via Integrations:OpenClaw:Password
- Gateway-Down → graceful degradation (HTTP 200, leere Daten)
- Build: 0 errors, Tests: 3/3 passed

backend/Program.cs

@@ -112,6 +112,13 @@ builder.Services.AddHttpClient("gateway", client =>
     client.Timeout = TimeSpan.FromSeconds(5);
 });
 
+builder.Services.AddHttpClient<OpenClawGatewayClient>(client =>
+{
+    client.BaseAddress = new(builder.Configuration["Integrations:OpenClaw:BaseUrl"]
+        ?? "http://127.0.0.1:18789");
+    client.Timeout = TimeSpan.FromSeconds(5);
+});
+
 // --- Application Services ---
 builder.Services.AddTransient<ModelRoutingService>();
 builder.Services.AddScoped<IAuthService, AuthService>();