fix(import): create placeholder category for orphan articles

app/Console/Commands/SablogImportCommand.php

@@ -213,6 +213,8 @@ class SablogImportCommand extends Command
                 }
             }
 
+            $this->ensureCategoryExists((int) $row->cid);
+
             $this->upsertWithId(Article::class, (int) $row->articleid, [
                 'category_id' => (int) $row->cid,
                 'user_id' => (int) $row->uid,
@@ -424,6 +426,32 @@ class SablogImportCommand extends Command
         return $model;
     }
 
+    /** @var array<int, bool> */
+    protected array $ensuredCategories = [];
+
+    /**
+     * 老库里可能存在已删除分类的孤儿文章，为其补一个占位分类以满足外键约束。
+     */
+    protected function ensureCategoryExists(int $cid): void
+    {
+        if ($cid <= 0 || isset($this->ensuredCategories[$cid])) {
+            return;
+        }
+
+        $this->ensuredCategories[$cid] = true;
+
+        if (Category::query()->whereKey($cid)->exists()) {
+            return;
+        }
+
+        $this->upsertWithId(Category::class, $cid, [
+            'name' => "已删除分类 {$cid}",
+            'display_order' => 9999,
+            'articles_count' => 0,
+        ]);
+        $this->warn("Category #{$cid} missing in source; placeholder created for orphan articles.");
+    }
+
     protected function countTable($source, string $table, string $key): void
     {
         if ($this->sourceTableExists($source, $table)) {