task: Verify HEIC/HEIF images don't attempt to be previewed

HEIF/HEIC previews should always have a fallback path (thumbnail + “download to view”) since browser support is spotty/nonexistent across major browsers

No files or tests are mentioned in the issue. Start by tracing where the UI decides to render image previews (thumbnail/image component and any file-type detection helpers), then locate the HEIC/HEIF handling path. Confirm that those formats should always use a fallback state with the thumbnail + download-to-view flow instead of inline preview. Run the project’s frontend test/build checks and manually verify with a HEIC/HEIF sample that no inline preview is attempted.

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