fix : code review — correct 15 issues across UX overhaul (phases 1-4)

Critical fixes:
- Make MigrateConstructeurLinks migration no-op (legacy tables already dropped)
- Add explicit ON CONFLICT (id) target in RestoreConstructeurLinks migration
- Replace N+1 queries with 4 bulk GROUP BY in ConstructeurStatsController
- Declare missing versionListRef template ref in machine detail page
- Add missing await on removeMachineDocument, cast activeTab as string

Important fixes:
- Add lang="ts" to ToastContainer and constructeurs page
- Type entityType as union in UsedInSection/useUsedIn
- Remove dead duration param from showError
- Update back-link props to new /catalogues/* URLs (3 pages)
- Replace raw error blocks with EmptyState in component/piece detail pages
- Type handleFillEntity params and machineInfoCardRef

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/app/components/common/UsedInSection.vue

@@ -38,7 +38,7 @@
 
 <script setup lang="ts">
 const props = defineProps<{
-  entityType: string
+  entityType: 'composants' | 'pieces' | 'products'
   entityId: string | null
 }>()