fix(covers): fallback to neutral prompt when title trips content moderation

input new_sensitive 的标题（自杀/逝世等）改用不含标题的通用提示词重试一次

app/Blog/Services/CoverGenerator.php

@@ -35,16 +35,13 @@ class CoverGenerator
         // 站点无常驻 queue worker：同步产出 card 转换，避免缩略图永远卡在队列里。
         config(['media-library.queue_conversions_by_default' => false]);
 
-        $response = Http::timeout(120)
-            ->withToken($this->llm->apiKey())
-            ->post($this->llm->baseUrl().'/image_generation', [
-                'model' => $this->model($model),
-                'prompt' => $this->buildPrompt($post, $style),
-                'aspect_ratio' => '16:9',
-                'response_format' => 'url',
-                'n' => 1,
-                'prompt_optimizer' => true,
-            ]);
+        $response = $this->requestImage($this->buildPrompt($post, $style), $model);
+
+        // 标题触发内容审核（input new_sensitive）：退化为不含标题的通用提示词重试一次。
+        if (str_contains((string) $response->body(), 'sensitive')
+            && ! is_string($response->json('data.image_urls.0'))) {
+            $response = $this->requestImage($this->neutralPrompt($style), $model);
+        }
 
         if ($response->failed()) {
             throw new \RuntimeException('HTTP '.$response->status().'：'.Str::limit($response->body(), 200));
@@ -91,4 +88,29 @@ class CoverGenerator
 
         return implode('。', $parts);
     }
+
+    /**
+     * 不含标题/摘要的通用封面提示词（标题触发审核时的兜底）。
+     */
+    public function neutralPrompt(?string $style = null): string
+    {
+        $style = trim((string) ($style
+            ?: blog_setting('cover_prompt_style', '扁平插画风格，色调柔和，构图简洁')));
+
+        return "博客文章封面配图。{$style}。画面中不要出现任何文字";
+    }
+
+    private function requestImage(string $prompt, ?string $model = null): \Illuminate\Http\Client\Response
+    {
+        return Http::timeout(120)
+            ->withToken($this->llm->apiKey())
+            ->post($this->llm->baseUrl().'/image_generation', [
+                'model' => $this->model($model),
+                'prompt' => $prompt,
+                'aspect_ratio' => '16:9',
+                'response_format' => 'url',
+                'n' => 1,
+                'prompt_optimizer' => true,
+            ]);
+    }
 }