feat(fc3c): migration 0013 — download_event.metadata + import_settings downloader fields

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

alembic/versions/0013_fc3c_download_event_metadata.py

@@ -0,0 +1,52 @@
+"""fc3c: download_event.metadata + import_settings downloader fields
+
+Revision ID: 0013
+Revises: 0012
+Create Date: 2026-05-20
+
+Additive only. download_event.metadata is the rich JSONB blob FC-3c
+populates per run (run_stats, stdout/stderr, quarantined paths, import
+summary). import_settings gains two operator-tunable downloader knobs:
+download_rate_limit_seconds (gallery-dl extractor.sleep) and
+download_validate_files (toggle the magic-byte validator).
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.dialects import postgresql
+
+revision: str = "0013"
+down_revision: Union[str, None] = "0012"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "download_event",
+        sa.Column(
+            "metadata", postgresql.JSONB,
+            nullable=False, server_default=sa.text("'{}'::jsonb"),
+        ),
+    )
+    op.add_column(
+        "import_settings",
+        sa.Column(
+            "download_rate_limit_seconds", sa.Float(),
+            nullable=False, server_default="3.0",
+        ),
+    )
+    op.add_column(
+        "import_settings",
+        sa.Column(
+            "download_validate_files", sa.Boolean(),
+            nullable=False, server_default=sa.true(),
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("import_settings", "download_validate_files")
+    op.drop_column("import_settings", "download_rate_limit_seconds")
+    op.drop_column("download_event", "metadata")