feat(config): añade Settings con Pydantic Settings y .env loading

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/unit/test_config.py

@@ -0,0 +1,21 @@
+"""Tests de configuración."""
+
+import os
+from pathlib import Path
+from unittest.mock import patch
+
+from agentforge_core.config import Settings
+
+
+def test_settings_defaults_seguros() -> None:
+    with patch.dict(os.environ, {}, clear=True):
+        s = Settings(_env_file=None)  # type: ignore[call-arg]
+        assert s.llm_provider == "mock"
+        assert s.guardrails_nemo_enabled is False
+        assert s.log_level == "INFO"
+
+
+def test_settings_data_dir_se_resuelve() -> None:
+    with patch.dict(os.environ, {"DATA_DIR": "/tmp/agentforge-test"}, clear=True):
+        s = Settings(_env_file=None)  # type: ignore[call-arg]
+        assert s.data_dir == Path("/tmp/agentforge-test")