- Fix production bug in send_whatsapp_message: access 'instance_url' instead
of 'server_url' to match SendMessageScheme TypedDict definition
- Update webhook test to use test_app with in-memory dependencies
- Mock send_whatsapp_message to avoid real HTTP calls in tests
- Add assertions to verify correct parameters passed to send_whatsapp_message
Bug: send_whatsapp_message accessed request_data['server_url'] but
SendMessageScheme defines field as 'instance_url', causing KeyError when
webhook tries to send WhatsApp messages.
- Add `_extract_mcp_content_text()` helper in naliia_tools.py to safely
extract text from MCP results, preventing IndexError on empty content
- Replace all direct `result.content[0].text` accesses with safe helper
- Improve customer identification with preservation of existing state
- Add proper JSON parsing with fallback and error handling
- Simplify webhook state management (use agent's checkpointer internally)
- Update system prompt to remove check_mcp_connection tool reference
- Fix tests to use async mocks and correct expected values
