Add find-me LED locate on master and slaves via ESP-NOW.

UART FIND_ME (client_id 0 = local ring, >0 = unicast), ESPNOW_FIND_ME payload, CLI/dashboard buttons per slave.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/api_serve.go

@@ -40,6 +40,16 @@ type unicastAPIResponse struct {
 	Error   string `json:"error,omitempty"`
 }
 
+type findMeAPIRequest struct {
+	ClientID uint32 `json:"client_id"`
+}
+
+type findMeAPIResponse struct {
+	Success  bool   `json:"success"`
+	ClientID uint32 `json:"client_id,omitempty"`
+	Error    string `json:"error,omitempty"`
+}
+
 type otaAPIResponse struct {
 	Success       bool   `json:"success"`
 	BytesWritten  uint32 `json:"bytes_written,omitempty"`
@@ -65,6 +75,13 @@ func mountServeAPI(mux *http.ServeMux, link *managedSerial, hub *wsHub) {
 		}
 		serveUnicastTest(w, r, link)
 	})
+	mux.HandleFunc("/api/find-me", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+		serveFindMe(w, r, link)
+	})
 	mux.HandleFunc("/api/ota", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
@@ -216,6 +233,22 @@ func applyDeadzoneToSlaves(link *managedSerial, deadzone uint32) (uint32, error)
 	return updated, nil
 }
 
+func serveFindMe(w http.ResponseWriter, r *http.Request, link *managedSerial) {
+	var body findMeAPIRequest
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeJSON(w, http.StatusBadRequest, findMeAPIResponse{Error: "invalid JSON"})
+		return
+	}
+	if err := link.FindMe(body.ClientID); err != nil {
+		writeJSON(w, http.StatusServiceUnavailable, findMeAPIResponse{
+			ClientID: body.ClientID,
+			Error:    err.Error(),
+		})
+		return
+	}
+	writeJSON(w, http.StatusOK, findMeAPIResponse{Success: true, ClientID: body.ClientID})
+}
+
 func serveUnicastTest(w http.ResponseWriter, r *http.Request, link *managedSerial) {
 	var body unicastAPIRequest
 	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {