fc5: migration 0015 + MigrationRun model (kind/status as String(32), API-validated)

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

backend/app/models/__init__.py

@@ -10,6 +10,7 @@ from .image_record import ImageRecord
 from .import_batch import ImportBatch
 from .import_settings import ImportSettings
 from .import_task import ImportTask
+from .migration_run import MigrationRun
 from .ml_settings import MLSettings
 from .post import Post
 from .post_attachment import PostAttachment
@@ -40,6 +41,7 @@ __all__ = [
     "ImportTask",
     "ImportSettings",
     "MLSettings",
+    "MigrationRun",
     "TagAlias",
     "TagAllowlist",
     "TagReferenceEmbedding",

backend/app/models/migration_run.py

@@ -0,0 +1,37 @@
+"""MigrationRun — tracks each FC-5 migration invocation (backup/gs/ir/etc).
+
+kind/status are String(32) not Postgres ENUM so adding kinds later
+doesn't need a schema migration. The API layer validates values.
+"""
+
+from datetime import datetime
+
+import sqlalchemy as sa
+from sqlalchemy import Boolean, DateTime, Integer, String, Text, func
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+
+class MigrationRun(Base):
+    __tablename__ = "migration_run"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    kind: Mapped[str] = mapped_column(String(32), nullable=False, index=True)
+    status: Mapped[str] = mapped_column(String(32), nullable=False, index=True)
+    dry_run: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    started_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now(),
+    )
+    finished_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True,
+    )
+    counts: Mapped[dict] = mapped_column(
+        JSONB, nullable=False, default=dict, server_default=sa.text("'{}'::jsonb"),
+    )
+    error: Mapped[str | None] = mapped_column(Text, nullable=True)
+    metadata_: Mapped[dict] = mapped_column(
+        "metadata", JSONB, nullable=False, default=dict,
+        server_default=sa.text("'{}'::jsonb"),
+    )