Validate vehicle type references across GBFS feeds

[mackenziereading19]

Fixes a subset of #217.

This adds cross-file validation ensuring vehicle_type_id values in free_bike_status.json / vehicle_status.json resolve to IDs defined in vehicle_types.json.

The check is applied across supported GBFS versions v2.1, v2.2, v2.3, v3.0 and v3.1-RC3.

Existing conditional behaviour requiring current_range_meters for motorized vehicle types is preserved.

A regression fixture demonstrates the previous false negative in GBFS v3.0, where an undefined vehicle_type_id passed validation without errors.

Tests

• full validator suite: 34 passed;
• snapshots: 7 passed;
• v3.0 undefined-reference regression: passed;
• structural checks across v2.1/v2.2/v2.3/v3.0/v3.1-RC3: passed.

This intentionally does not yet address the other cross-file ID relationships mentioned in #217, such as station, pricing-plan or geofencing references.

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[richfab]

Hello @mackenziereading19,

Thank you for contributing to the GBFS validator!

Sorry for the delayed response.

As explained in #217, I think that if we add object dependency relationships validation, we should do it for all objects.

I will check internally with MobilityData IT team how we can help with this. Please note that this Javascript validator will progressively be replaced by this one in Java: https://github.com/MobilityData/gbfs-validator-java.

Best regards,
Fabien (MobilityData)

cc @davidgamez @emmambd

[richfab]

Hello @mackenziereading19,

Thank you for your contribution to the JavaScript validator.

As explained in #217, we want to refrain from approving PRs with partial fixes, since we won't have time to follow up and complete them.

For now, I will close this PR, the conversation continues in #153.

Please don't hesitate if you have any questions.

Thank you!
Fabien (MobilityData)