feat: add all application source code

- apps/api: FastAPI backend with Dockerfile
- apps/web: Next.js frontend with Dockerfile
- apps/sensor: Signal collection agent
- packages: shared packages

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

apps/api/src/config.py

@@ -0,0 +1,4 @@
+# Backward compatibility - re-export from core.config
+from src.core.config import Settings, settings, get_settings
+
+__all__ = ["Settings", "settings", "get_settings"]