Unify start commands

> [!NOTE]
> Migrated from [augurlabs/augur#3618](https://github.com/augurlabs/augur/issues/3618)
> Originally opened by `@MoralCode` on 2026-01-21

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`augur backend start` essentially starts up both the API and the collection.

it does this with one giant function that duplicates the behavior of the api and collection start commands

meaning if we wanted to update how the startup works we need to update things in two places

tech debt alert

pointed out by @ABrain7710