Validate project device drop targets

src/domain/services/project-device-placement.service.ts

@@ -0,0 +1,29 @@
+export interface ProjectDevicePlacementSource {
+  category?: string | null;
+  phaseType: "single_phase" | "three_phase";
+}
+
+export interface ProjectDevicePlacementSection {
+  key: string;
+}
+
+export type DefaultCircuitSectionKey = "lighting" | "single_phase" | "three_phase";
+
+// Lighting classification takes precedence over the electrical phase because
+// lighting devices use their dedicated numbering section by default.
+export function inferProjectDeviceSectionKey(
+  device: ProjectDevicePlacementSource
+): DefaultCircuitSectionKey {
+  const category = (device.category ?? "").trim().toLowerCase();
+  if (category.includes("light") || category.includes("beleuchtung")) {
+    return "lighting";
+  }
+  return device.phaseType;
+}
+
+export function isProjectDevicePlacementValid(
+  device: ProjectDevicePlacementSource,
+  section: ProjectDevicePlacementSection
+): boolean {
+  return section.key === inferProjectDeviceSectionKey(device);
+}