add seed ability

README.md

@@ -19,8 +19,25 @@ Open <http://127.0.0.1:3000>. The application creates `sustenance.db` in the wor
 | `PUBLIC_BASE_URL` | derived from `BIND_ADDRESS` | Base URL used in invitation links |
 | `COOKIE_SECURE` | `false` | Add the `Secure` attribute to session cookies |
 | `REGISTRATION_MODE` | `invite_only` | Use `open` for local development; otherwise registration requires a valid list invitation after the first account |
+| `SEED_CONFIG` | `seed.json` | Optional JSON file with a default user to create when the database is first initialized |
 | `RUST_LOG` | `sustenance=debug,tower_http=info` | Log filter |
 
+### Seeding a default user
+
+If a JSON config file exists at the path given by `SEED_CONFIG` (default `seed.json`),
+Sustenance creates the configured user on startup when the database has no users yet.
+The file is optional — if it is missing or invalid, seeding is silently skipped.
+
+```json
+{
+  "user": {
+    "email": "you@example.com",
+    "display_name": "You",
+    "password": "a-strong-password"
+  }
+}
+```
+
 ## Current features
 
 - Email/password accounts with Argon2 password hashes