fix: empty JSON arrays instead of null for alerts/events/runs

backend/internal/api/alerts.go

@@ -5,6 +5,8 @@ import (
 	"net/http"
 	"strconv"
 
+	"flowsight/internal/store"
+
 	"github.com/go-chi/chi/v5"
 )
 
@@ -15,6 +17,9 @@ func (s *Server) ListAlerts(w http.ResponseWriter, r *http.Request) {
 		writeErr(w, http.StatusBadGateway, "db: "+err.Error())
 		return
 	}
+	if rows == nil {
+		rows = []store.Alert{}
+	}
 	writeJSON(w, http.StatusOK, map[string]any{"alerts": rows})
 }
 
@@ -72,5 +77,8 @@ func (s *Server) AlertEvents(w http.ResponseWriter, r *http.Request) {
 		writeErr(w, http.StatusBadGateway, "db: "+err.Error())
 		return
 	}
+	if evts == nil {
+		evts = []map[string]any{}
+	}
 	writeJSON(w, http.StatusOK, map[string]any{"events": evts})
 }

backend/internal/api/routines.go

@@ -101,6 +101,9 @@ func (s *Server) RunHistory(w http.ResponseWriter, r *http.Request) {
 		writeErr(w, http.StatusBadGateway, "db: "+err.Error())
 		return
 	}
+	if hist == nil {
+		hist = []map[string]any{}
+	}
 	writeJSON(w, http.StatusOK, map[string]any{"runs": hist})
 }