Add isolated staging and synthetic weather workflow

README.md

@@ -10,6 +10,16 @@ Rename `.env-sample` to `.env` and fill in credentials
 docker-compose up --build --no-cache --force-recreate
 ```
 
+## Local synthetic weather data
+
+The local database can be populated with deterministic hourly sample data for all 33 stations. The seed covers the previous 18 months through the current hour and can be run repeatedly without creating duplicates.
+
+```sh
+docker compose --profile tools run --rm seed
+```
+
+This workflow is intended only for development and UI testing. It uses the normal `weather` table and application APIs; it does not provide LVGMC forecast CSV or HARMONIE GRIB fixtures.
+
 ## Web
 [http://0.0.0.0:9090/](http://0.0.0.0:9090/)
 
@@ -68,4 +78,4 @@ df -h
 
 ```
 fly scale memory 512
-```
+```