feat(fc3b): migration 0012 + AppSetting model

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

alembic/versions/0012_fc3b_app_setting.py

@@ -0,0 +1,36 @@
+"""fc3b: app_setting key/value table
+
+Revision ID: 0012
+Revises: 0011
+Create Date: 2026-05-20
+
+A simple key/value table for small app settings that don't fit
+ImportSettings. Initially seeds only `extension_api_key` (done in
+create_app on first boot — not in the migration, to keep it
+deterministic and independent of randomness).
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0012"
+down_revision: Union[str, None] = "0011"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "app_setting",
+        sa.Column("key", sa.String(length=64), primary_key=True),
+        sa.Column("value", sa.Text(), nullable=False),
+        sa.Column(
+            "updated_at", sa.DateTime(timezone=True),
+            nullable=False, server_default=sa.func.now(),
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_table("app_setting")