feat(ui) : add UsedInSection showing reverse entity relationships on detail pages

frontend/app/components/common/UsedInSection.vue

@@ -0,0 +1,49 @@
+<template>
+  <div v-if="!loading && totalCount > 0" class="space-y-3 rounded-lg border border-base-200 bg-base-200/30 p-4">
+    <h3 class="font-semibold text-base-content">Utilisé dans</h3>
+
+    <div v-if="data.machines.length" class="space-y-1">
+      <p class="text-xs font-medium text-base-content/60 uppercase tracking-wide">Machines</p>
+      <div v-for="m in data.machines" :key="m.id" class="flex items-center gap-2 text-sm">
+        <NuxtLink :to="`/machine/${m.id}`" class="hover:underline hover:text-primary transition-colors font-medium">
+          {{ m.name }}
+        </NuxtLink>
+        <span v-if="m.site?.name" class="badge badge-ghost badge-xs">{{ m.site.name }}</span>
+      </div>
+    </div>
+
+    <div v-if="data.composants.length" class="space-y-1">
+      <p class="text-xs font-medium text-base-content/60 uppercase tracking-wide">Composants</p>
+      <div v-for="c in data.composants" :key="c.id" class="text-sm">
+        <NuxtLink :to="`/component/${c.id}`" class="hover:underline hover:text-primary transition-colors font-medium">
+          {{ c.name }}
+        </NuxtLink>
+      </div>
+    </div>
+
+    <div v-if="data.pieces.length" class="space-y-1">
+      <p class="text-xs font-medium text-base-content/60 uppercase tracking-wide">Pièces</p>
+      <div v-for="p in data.pieces" :key="p.id" class="text-sm">
+        <NuxtLink :to="`/piece/${p.id}`" class="hover:underline hover:text-primary transition-colors font-medium">
+          {{ p.name }}
+        </NuxtLink>
+      </div>
+    </div>
+  </div>
+
+  <div v-else-if="loading" class="flex justify-center py-4">
+    <span class="loading loading-spinner loading-sm" />
+  </div>
+</template>
+
+<script setup lang="ts">
+const props = defineProps<{
+  entityType: string
+  entityId: string | null
+}>()
+
+const { data, loading, totalCount } = useUsedIn(
+  computed(() => props.entityType),
+  computed(() => props.entityId),
+)
+</script>

frontend/app/composables/useUsedIn.ts

@@ -0,0 +1,52 @@
+import type { Ref } from 'vue'
+
+interface UsedInMachine {
+  id: string
+  name: string
+  site?: { id: string; name: string } | null
+}
+
+interface UsedInEntity {
+  id: string
+  name: string
+}
+
+interface UsedInData {
+  machines: UsedInMachine[]
+  composants: UsedInEntity[]
+  pieces: UsedInEntity[]
+}
+
+export function useUsedIn(entityType: Ref<string>, entityId: Ref<string | null>) {
+  const data = ref<UsedInData>({ machines: [], composants: [], pieces: [] })
+  const loading = ref(false)
+
+  const api = useApi()
+
+  const load = async () => {
+    if (!entityId.value) return
+    loading.value = true
+    try {
+      const result = await api.get(`/${entityType.value}/${entityId.value}/used-in`)
+      if (result.success && result.data) {
+        data.value = {
+          machines: result.data.machines || [],
+          composants: result.data.composants || [],
+          pieces: result.data.pieces || [],
+        }
+      }
+    } finally {
+      loading.value = false
+    }
+  }
+
+  const totalCount = computed(() =>
+    data.value.machines.length + data.value.composants.length + data.value.pieces.length
+  )
+
+  watch(entityId, (val) => {
+    if (val) load()
+  }, { immediate: true })
+
+  return { data, loading, totalCount, load }
+}

frontend/app/pages/component/[id]/index.vue

@@ -198,6 +198,8 @@
                     </p>
                   </div>
                 </div>
+
+                <CommonUsedInSection entity-type="composants" :entity-id="component?.id ?? null" />
               </div>
             </template>
 

frontend/app/pages/piece/[id].vue

@@ -222,6 +222,8 @@
                   :preview-badge="formatPieceStructurePreview(resolvedStructure)"
                   variant="piece"
                 />
+
+                <CommonUsedInSection entity-type="pieces" :entity-id="piece?.id ?? null" />
               </div>
             </template>
 

frontend/app/pages/product/[id]/index.vue

@@ -198,6 +198,8 @@
                     <span class="badge badge-outline">{{ structurePreview }}</span>
                   </div>
                 </div>
+
+                <CommonUsedInSection entity-type="products" :entity-id="product?.id ?? null" />
               </div>
             </template>