Validating ParsedMedia.data is not empty

[jamesbraza]

Enabling client code to avoid if media.data checks

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Note

Strengthens media validation to prevent empty image payloads.

• Update ParsedMedia.data in types.py to require min_length=1 (non-empty bytes)
• Add test_parsed_media_empty_data_raises asserting ValidationError for empty data

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[maykcaldas]

lgtm