fc5: ml_queue (fire tag_and_embed for unprocessed) + verify (row counts + sha256 sample)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/services/migrators/ml_queue.py

@@ -0,0 +1,21 @@
+"""Queue every migrated image_record with no embedding for ML re-processing."""
+from __future__ import annotations
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from ...models import ImageRecord
+
+
+async def queue_all_unprocessed_async(db: AsyncSession) -> int:
+    """Find every ImageRecord with siglip_embedding IS NULL, fire
+    tag_and_embed.delay(id) for each. Returns count queued.
+    """
+    from ...tasks.ml import tag_and_embed
+
+    rows = (await db.execute(
+        select(ImageRecord.id).where(ImageRecord.siglip_embedding.is_(None))
+    )).scalars().all()
+    for image_id in rows:
+        tag_and_embed.delay(image_id)
+    return len(rows)