Fix AI extraction JSON-LD parsing and add debug logging

- Extract JSON-LD scripts BEFORE removing script tags
- Add logging for prepared HTML, AI responses, and parsed data
- Include more detailed error messages in test endpoint

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/routes/settings.ts

@@ -199,16 +199,21 @@ router.post('/ai/test', async (req: AuthRequest, res: Response) => {
       return;
     }
 
+    console.log(`[AI Test] Testing URL: ${url} with provider: ${settings.ai_provider}`);
+
     const { extractWithAI } = await import('../services/ai-extractor');
     const result = await extractWithAI(url, settings);
 
+    console.log(`[AI Test] Result:`, JSON.stringify(result, null, 2));
+
     res.json({
       success: !!result.price,
       ...result,
     });
   } catch (error) {
     console.error('Error testing AI extraction:', error);
-    res.status(500).json({ error: 'Failed to test AI extraction' });
+    const errorMessage = error instanceof Error ? error.message : 'Unknown error';
+    res.status(500).json({ error: `Failed to test AI extraction: ${errorMessage}` });
   }
 });