feat(regions): image_region storage + service for the crop pipeline (#114 slice 2)

The storage backbone both crop jobs write to and read from. image_region =
normalized bbox (rx/ry/rw/rh) + kind ('face'/'figure' → CCIP character id;
'concept' → SigLIP head bag) + the crop's embedding (nullable Vector(768) CCIP /
Vector(1152) SigLIP, one per kind) + version stamps for compute-once gating. The
bbox doubles as grounded-tag provenance. Migration 0061.

RegionService.replace_regions (scoped BY KIND so the figure + concept pipelines
don't clobber each other) + get_regions — the GPU agent's results endpoint will
call the writer; the character matcher + bag scorer read. Server-side, no GPU.

Tests: replace/get round-trip, kind-scoped replacement, CCIP vector round-trip.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

backend/app/models/__init__.py

@@ -15,6 +15,7 @@ from .head_training_run import HeadTrainingRun
 from .image_prediction import ImagePrediction
 from .image_provenance import ImageProvenance
 from .image_record import ImageRecord
+from .image_region import ImageRegion
 from .import_batch import ImportBatch
 from .import_settings import ImportSettings
 from .import_task import ImportTask
@@ -60,6 +61,7 @@ __all__ = [
     "ImageRecord",
     "ImagePrediction",
     "ImageProvenance",
+    "ImageRegion",
     "Tag",
     "TagKind",
     "image_tag",

backend/app/models/image_region.py

@@ -0,0 +1,57 @@
+"""ImageRegion — a detected/proposed sub-region of an image + its crop embedding.
+
+The storage backbone of the crop pipeline (#114). A region is a normalized bbox
+plus the embedding of its crop:
+- kind='face' / 'figure' → embedded by CCIP for cross-artist character identity.
+- kind='concept' → embedded by SigLIP, a localized instance for a concept head's
+  bag-of-embeddings (a concept is "present if ANY instance matches").
+One row carries the embedding appropriate to its kind (the other is null). The
+bbox doubles as grounded-tag provenance (hover a tag → highlight its region; a
+wrong box is a precise negative). The GPU agent writes these via the job API;
+the few-shot character matcher + bag scorer read them — both server-side, no GPU.
+"""
+
+from datetime import datetime
+
+from pgvector.sqlalchemy import Vector
+from sqlalchemy import DateTime, Float, ForeignKey, Integer, String, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+CCIP_DIM = 768       # deepghs/imgutils CCIP character embedding
+SIGLIP_DIM = 1152    # matches image_record.siglip_embedding
+
+
+class ImageRegion(Base):
+    __tablename__ = "image_region"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    image_record_id: Mapped[int] = mapped_column(
+        ForeignKey("image_record.id", ondelete="CASCADE"), index=True
+    )
+    # 'face' | 'figure' (→ CCIP character id) | 'concept' (→ SigLIP head bag).
+    kind: Mapped[str] = mapped_column(String(16), nullable=False)
+    # Normalized bbox in [0,1]: top-left (rx, ry) + size (rw, rh). Named rx/ry/…
+    # rather than x/y/by to dodge SQL keyword ambiguity ('by').
+    rx: Mapped[float] = mapped_column(Float, nullable=False)
+    ry: Mapped[float] = mapped_column(Float, nullable=False)
+    rw: Mapped[float] = mapped_column(Float, nullable=False)
+    rh: Mapped[float] = mapped_column(Float, nullable=False)
+    # Proposer/detector confidence (null for deterministic proposers).
+    score: Mapped[float | None] = mapped_column(Float, nullable=True)
+    # Version stamps so a re-detect / re-crop / re-embed can be gated (compute
+    # once; only redo when the producing model version changes).
+    detector_version: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    crop_version: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    embedding_version: Mapped[str | None] = mapped_column(String(128), nullable=True)
+    # Exactly one is set, per kind.
+    ccip_embedding: Mapped[list[float] | None] = mapped_column(
+        Vector(CCIP_DIM), nullable=True
+    )
+    siglip_embedding: Mapped[list[float] | None] = mapped_column(
+        Vector(SIGLIP_DIM), nullable=True
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )