`weather-mv`: Automatic database migrations

As a user, when I run a newer version of `weather-mv` on a dataset, and the schema of the BigQuery database has changed (i.e. changed wrt to the dataset), I would like `weather-mv` to automatically migrate the table. I need this, as a user, so I don't my data pipelines don't break when new versions of `weather-mv` are released, and so I can get the latest tool features.

Last, as a user, I would like some control over weather migrations are applied, and what migrations to make. Ideally, the CLI should let me opt out of migrations if I know best. Otherwise, I want the tools to default to the recommended case.

Start by locating the `weather-mv` CLI and its BigQuery schema handling. Define how schema changes and migration versions should be detected, how recommended migrations and opt-out controls should work, and how completion will preserve existing data pipelines while enabling newer tool features.

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