chore(docker): add containerized development setup

README.md

@@ -66,6 +66,24 @@ npm run dev
 
 The frontend is available at `http://127.0.0.1:3000`. The backend health endpoint is available at `http://127.0.0.1:8080/health`.
 
+## Running with Docker Compose
+
+Create the root `.env` file as described in the configuration section, then build and start both services:
+
+```powershell
+docker compose up --build
+```
+
+Open `http://localhost:3000` in your browser. The API is exposed at `http://localhost:8080`, and SQLite data is kept in the named `card_to_iban_data` volume.
+
+Stop the services with:
+
+```powershell
+docker compose down
+```
+
+The database volume is preserved by default. To remove it intentionally, run `docker compose down --volumes`.
+
 ## API Contract
 
 ### Convert a card number to an IBAN