AI Analysis: clean extracted text to prevent JSON encoding errors

app/Services/AIAnalysisService.php

@@ -50,13 +50,28 @@ class AIAnalysisService
 
         try {
             $pdf = $this->parser->parseFile(Storage::disk('local')->path($document->file_path));
-            return $pdf->getText();
+            $text = $pdf->getText();
+            return $this->cleanText($text);
         } catch (\Exception $e) {
             Log::error("PDF Extraction Error: " . $e->getMessage());
             return null;
         }
     }
 
+    /**
+     * Clean text to ensure it's valid UTF-8 and fits well in JSON.
+     */
+    protected function cleanText(string $text): string
+    {
+        // Remove non-UTF8 characters
+        $text = mb_convert_encoding($text, 'UTF-8', 'UTF-8');
+        
+        // Remove control characters (except newlines and tabs)
+        $text = preg_replace('/[^\x20-\x7E\xA0-\xFF\x0A\x0D\x09]/u', '', $text);
+        
+        return trim($text);
+    }
+
     /**
      * Call the AI API (using a placeholder for now, or direct Http call).
      */