Implement radar-telemt-dcs aggregation endpoint and UI integration

- Added new API route `/api/agg/radar-telemt-dcs` to aggregate DC status data from multiple upstreams, including metrics like coverage percentage and RTT.
- Implemented handler logic in `handlers.go` and corresponding tests in `handlers_test.go` to ensure correct data retrieval and response formatting.
- Updated the frontend to fetch and display radar DC data, enhancing the user interface with a new section for Telemt ME snapshots.
- Enhanced documentation in `AGGREGATE.md` and `README.md` to reflect the new functionality and usage details.

internal/aggregate/handlers_test.go

@@ -113,6 +113,65 @@ func TestHandlerFleetStatus(t *testing.T) {
 	}
 }
 
+func TestHandlerRadarTelemtDcs(t *testing.T) {
+	up := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/v1/stats/dcs" {
+			http.NotFound(w, r)
+			return
+		}
+		_ = json.NewEncoder(w).Encode(map[string]any{
+			"ok": true,
+			"data": map[string]any{
+				"middle_proxy_enabled":     true,
+				"generated_at_epoch_secs":  1,
+				"dcs": []map[string]any{{
+					"dc": 1, "rtt_ms": 42.5, "coverage_pct": 100.0,
+					"alive_writers": 3, "required_writers": 3, "load": 0,
+				}},
+			},
+			"revision": "rd",
+		})
+	}))
+	defer up.Close()
+
+	cfg := &config.Config{
+		Servers: []config.Server{
+			{Alias: "test", BaseURL: up.URL, PathPrefix: "/v1"},
+		},
+	}
+	if err := cfg.Validate(); err != nil {
+		t.Fatal(err)
+	}
+	parsed, err := cfg.Parse()
+	if err != nil {
+		t.Fatal(err)
+	}
+	h := NewHandler(parsed, up.Client(), nil, 0)
+	req := httptest.NewRequest(http.MethodGet, "/api/agg/radar-telemt-dcs?aliases=test", nil)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status %d body %s", rec.Code, rec.Body.String())
+	}
+	var env struct {
+		OK   bool             `json:"ok"`
+		Data RadarTelemtDcsData `json:"data"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &env); err != nil {
+		t.Fatal(err)
+	}
+	if !env.OK || len(env.Data.Servers) != 1 {
+		t.Fatalf("envelope: %+v", env)
+	}
+	row := env.Data.Servers[0]
+	if row.Alias != "test" || !row.OK || row.Data == nil || !row.Data.MiddleProxyEnabled {
+		t.Fatalf("row: %+v", row)
+	}
+	if len(row.Data.Dcs) != 1 || row.Data.Dcs[0].DC != 1 {
+		t.Fatalf("dcs: %+v", row.Data.Dcs)
+	}
+}
+
 func TestHandlerUserOne(t *testing.T) {
 	up := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.URL.Path != "/v1/stats/users" {