Capture Object.width/height for GIF uploads (#690 phase 1)

[vjpixel]

Summary

Phase 1 of #690 — capture native pixel dimensions for raster uploads on Object. Lays the groundwork for thumbnails and AR/MR rendering to use real dimensions (refs #473, #319) instead of the hardcoded 50×50 in Object.as_html_thumbnail.

Scope is intentionally minimal: only GIF, only via Pillow (already in deps). MP4/WebM (ffprobe) and GLB (pygltflib/trimesh) are deferred — see my comment on the issue for the phased breakdown.

Changes

• Model: Object.width and Object.height (PositiveIntegerField(null=True, blank=True)).
• Migration: core.0028 adds the fields. objectevent (pghistory tracking model) gets the same fields automatically.
• Form: UploadObjectForm.save() populates width/height when file_extension == "gif". Other extensions leave the fields null until phase 2/3.
• Management command: backfill_object_dimensions for legacy rows. Iterates GIF rows where width__isnull=True, probes via Pillow, supports --dry-run, logs failures and skips unreadable files.

Verified locally

>>> form = UploadObjectForm(files={"source": <320×240 GIF>}, data={...})
>>> form.is_valid(); obj = form.save(commit=False); obj.owner = profile; obj.save()
saved: width=320, height=240, ext=gif

Risk

• Backward compat: fields are nullable; legacy rows have null until backfill runs.
• Phase 2/3: depend on ffmpeg + ffprobe (system deps) and a GLB parser. Out of scope here.
• No template change: nothing reads width/height yet. The follow-up to use these in the AR/MR rendering will arrive once the data is actually populated.

Test plan

• make test passes
• make migrate applies cleanly
• Upload a GIF → row has width/height set
• Upload an mp4 → row has width/height null (expected, phase 2)
• python src/manage.py backfill_object_dimensions --dry-run reports counts without saving
• python src/manage.py backfill_object_dimensions populates dimensions for existing GIFs

Refs #690 (phase 1)

https://claude.ai/code/session_01XC1THLWgnGXGf5wgRhdyvB

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Generated by Claude Code

[pablodiegoss]

We don't have access to run management commands on our servers. This should be implemented as a migration with python operations to populate the missing fields for older records, we have a few examples of this.

This ensures that after the new migrations run, fields are created, older records have the new fields populated and the new code should ensure that new records always populate the field through tests