fix: ensure database directory exists

backend/database.py

@@ -1,7 +1,25 @@
+"""Database configuration for the NodeProbe backend.
+
+This module sets up the SQLAlchemy engine and session factory.  It ensures the
+SQLite database file lives inside the repository's ``data`` directory regardless
+of the current working directory from which the application is launched.  The
+directory is created automatically if it does not already exist so that hitting
+API endpoints such as ``/tests`` doesn't fail with a missing database error.
+"""
+
+from pathlib import Path
+
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker, declarative_base
 
-DATABASE_URL = "sqlite:///./data/nodeprobe.db"
+# Determine an absolute path to the ``data`` directory (two levels up from this
+# file) and ensure it exists.  This allows the backend to run from any working
+# directory or Docker context without failing to locate the database file.
+BASE_DIR = Path(__file__).resolve().parent.parent
+DATA_DIR = BASE_DIR / "data"
+DATA_DIR.mkdir(parents=True, exist_ok=True)
+
+DATABASE_URL = f"sqlite:///{DATA_DIR / 'nodeprobe.db'}"
 
 engine = create_engine(
     DATABASE_URL, connect_args={"check_same_thread": False}