chore(lint): enable strict ESLint rules and fix unused-vars violations (F4.1)

Enable no-console (warn, allow error), @typescript-eslint/no-unused-vars
(warn, ignore _ prefix), and @typescript-eslint/no-explicit-any (warn).
Fix all 26 no-unused-vars violations across 9 files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/components/StructureNodeEditor.vue

@@ -541,7 +541,7 @@ const getPieceTypeLabel = (id?: string) => {
   return formatModelTypeOption(pieceTypeMap.value.get(id))
 }
 
-const getProductTypeLabel = (id?: string) => {
+const _getProductTypeLabel = (id?: string) => {
   if (!id) return ''
   return formatModelTypeOption(productTypeMap.value.get(id))
 }