Major changes: logic add to panel, local variables, panel histor, users management...

internal/dsp/nodes.go

@@ -204,6 +204,34 @@ func (n *DerivativeNode) Process(inputs []float64, state map[string]any) (float6
 	return 0, nil
 }
 
+// ── IntegrateNode ─────────────────────────────────────────────────────────────
+
+// IntegrateNode accumulates the time-integral of input[0] using the trapezoidal
+// rule, where dt is in seconds. On the first call it returns 0 (no interval yet).
+type IntegrateNode struct{}
+
+func (n *IntegrateNode) Type() string { return "integrate" }
+func (n *IntegrateNode) Process(inputs []float64, state map[string]any) (float64, error) {
+	if len(inputs) == 0 {
+		return 0, errors.New("integrate: no inputs")
+	}
+	now := time.Now()
+	acc, _ := state["acc"].(float64)
+	if prevVal, ok := state["prev_val"].(float64); ok {
+		if prevTime, ok := state["prev_time"].(time.Time); ok {
+			dt := now.Sub(prevTime).Seconds()
+			if dt < 0 {
+				dt = 0
+			}
+			acc += (inputs[0] + prevVal) * 0.5 * dt
+		}
+	}
+	state["acc"] = acc
+	state["prev_val"] = inputs[0]
+	state["prev_time"] = now
+	return acc, nil
+}
+
 // ── ClampNode ─────────────────────────────────────────────────────────────────
 
 // ClampNode clamps the output to [Min, Max].