refactor: reorganize aitbc core library into subpackages

- Create aitbc/crypto/ subpackage (crypto.py, security.py)
- Create aitbc/utils/ subpackage (validation, time_utils, json_utils, paths, env)
- Create aitbc/network/ subpackage (http_client, web3_utils)
- Update all import statements across codebase
- Maintain backward compatibility with __init__.py exports
- Improve code organization and modularity

cli/extended_features.py

@@ -2,7 +2,7 @@ import json
 import os
 import time
 import uuid
-from aitbc.paths import get_data_path
+from aitbc.utils.paths import get_data_path
 
 STATE_FILE = str(get_data_path("data/cli_extended_state.json"))