Fix IIIF manifest output for IIIF Image API v3

[joecorall]

What does this Pull Request do?

This updates islandora_iiif manifest generation to emit consistent Image API metadata for both IIIF Image API 2 and 3 services.

What's new?

• Detect Image API version from the IIIF service URL
• Emit the correct service @context / profile for:
  • /iiif/2/
  • /iiif/3/
• Use the correct painted image URL for v3:
  • v2: /full/full/0/default.jpg
  • v3: /full/max/0/default.jpg
• Add explicit canvas thumbnails
• Keep painted image format aligned with the declared JPEG derivative URL
• Extract URL/service helper logic for testability
• Add regression tests covering v2/v3 service metadata and URL generation

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• Reproduce the problem you are fixing (if applicable)
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Documentation Status

• Does this change existing behaviour that's currently documented?
• Does this change require new pages or sections of documentation?
• Who does this need to be documented for?
• Associated documentation pull request(s): ___ or documentation issue ___

Additional Notes:

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PR.

Interested parties

[aOelschlager]

I tested this and this works.