Add detailed error logging to debug GraphRAG issues

🤖 Generated with [Claude Code](https://claude.ai/code)

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

app.py

@@ -201,9 +201,13 @@ class BorgesGraphRAG:
             }
 
         except Exception as e:
+            import traceback
+            error_details = traceback.format_exc()
+            print(f"🚨 Full GraphRAG error: {error_details}")
             return {
                 "success": False,
                 "error": f"GraphRAG error: {str(e)}",
+                "error_details": error_details,
                 "book_id": self.current_book or "unknown",
                 "mode": mode,
                 "query": query