Add db migration and DNS dmarc entries

docs/runtime.md

@@ -32,7 +32,7 @@ There is no repository-local Ruff configuration or requirement in `requirements.
 The Docker image starts the FastAPI app with:
 
 ```bash
-uvicorn app.main:app --host 0.0.0.0 --port 8000
+alembic upgrade head && uvicorn app.main:app --host 0.0.0.0 --port 8000
 ```
 
 The compose service:
@@ -45,6 +45,13 @@ The compose service:
 - attaches to the external `npm_proxy` network with static address `192.168.99.18`.
 
 The app initializes database tables on import through `app.main` calling `init_db()`.
+Alembic migrations are run first in Docker and are the preservation path for existing SQLite databases. `init_db()` remains as a lightweight fallback for missing tables in local/test workflows.
+
+Manual migration command inside the container:
+
+```bash
+docker compose exec dmarc-sentinel alembic upgrade head
+```
 
 ## CLI Backlog Processing