Add EXIF object template covering key and raw metadata

[adulau]

Motivation

• Add a reusable EXIF object to support extracting and storing image metadata during ingestion and analysis as discussed in issues Extract Exif data from picture on ingestion #478 and EXIF extension object #483.
• Provide both a compact, analyst-friendly set of high-value EXIF fields and a raw-output attribute so ingestion pipelines can attach full extractor output.

Description

• Add a new object definition at objects/exif/definition.json with name: exif, meta-category: file, a generated uuid, and version: 1.
• Define attributes for timestamps, camera/device (make, model), lens/exposure (f-number, exposure-time, focal-length, flash), descriptive fields (image-description, artist, copyright, user-comment), processing info (software, tool, raw-output) and GPS fields (gps-latitude, gps-longitude, gps-altitude, gps-date-stamp).
• Mark a minimal ingest/analyst subset via ui-priority: 1 for attachment, datetime-original, make, model, gps-latitude, gps-longitude, and raw-output and allow creation when one of attachment, raw-output, datetime-original, or model is present (requiredOneOf).

Testing

• Ran ./validate_all.sh, which failed in this environment due to a missing external helper (uuidparse) and not because of the new template itself.
• Ran ./jq_all_the_things.sh to normalize and validate JSON formatting in-repo, which completed successfully.
• Confirmed the new objects/exif/definition.json file is present and well-formed JSON via direct inspection.

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Codex Task