feat(api): Add endpoint for returning pipeline version

[iambriccardo]

This PR introduces a new endpoint that returns version information for a pipeline.
The response includes:

• the current version under version, and
• a new_version field, populated when a newer version is available. A newer version is defined as a default image different from the current one.

The frontend can use this information to prompt the customer to update the pipeline version whenever an upgrade is possible, showing them the version information.

The endpoint also returns the version id to ensure that any update procedure is based on the version explicitly returned, rather than naively defaulting to the latest available version which could cause race conditions.

In the design we purposefully hide any mention of images, since we want to abstract the running environment of the pipeline and mentioning images might confuse people not familiar with K8S.

[coveralls]

Pull Request Test Coverage Report for Build 17463404362

Warning: This coverage report may be inaccurate.

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Details

• 76 of 77 (98.7%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 80.154%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
etl-api/src/utils.rs	41	42	97.62%

Totals
Change from base Build 17459033077:	0.1%
Covered Lines:	10735
Relevant Lines:	13393

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💛 - Coveralls