Offer guidance as to what to do after creating a new GTM container

## Feature Description

Currently when a new GTM container is created via Site Kit it won't be very useful. In fact it will actually raise a 404 on the homepage because the new container won't have any published version associated with it.

After a new container is created, we should offer some next steps for the user to take or learn about to use their new container.

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## Acceptance criteria

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## Implementation Brief

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### Test Coverage

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### Visual Regression Changes

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## QA Brief

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## Changelog entry

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The issue names no files, tests, or entry points. Start by locating the Site Kit flow that creates a new GTM container and determine where post-creation guidance is rendered. Done means users receive clear next steps after creating a container.

Written by the indexing model from the issue text.