Title: Investigate handling and reporting of unsupported HEIC media files

Context
During an Imagify audit, the Media Library reported one optimization error. Investigation showed that the affected file was:

File: wordpress-pizza-boxes.heic
Format: HEIC
Displayed status: "This media is not supported."

Problem
The unsupported HEIC file appears to be included in the optimization error count, which may make the statistics misleading. Users may also lack clear guidance on how to handle unsupported formats.

Expected outcome

Investigate and determine whether we should:

• Exclude unsupported formats from the optimization error count or classify them separately.
• Provide clearer messaging explaining why the format is unsupported.
• Offer guidance to convert the file to a supported format, if appropriate.
• Confirm whether HEIC support should be considered as a future enhancement.

Acceptance criteria

• Confirm how unsupported formats are classified in optimization statistics.
• Document the expected behavior for HEIC files.
• Decide whether any UI, documentation, or statistics changes are required.

Reproduce the case using wordpress-pizza-boxes.heic in the Media Library, then trace how unsupported media is classified in optimization statistics and how the current message is presented. Confirm the expected HEIC behavior and record whether UI, documentation, or statistics changes are required.