feat(billing): pilot user backfill — set existing accounts to complimentary

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/alembic/versions/c6cbfc534fad_subscriptions_pilot_complimentary_.py

@@ -0,0 +1,47 @@
+"""subscriptions pilot complimentary backfill
+
+This migration converts existing pilot/dev accounts to permanent complimentary
+Pro per the self-serve signup spec section 5. Forward-only; downgrade is
+prohibited because original status is not preserved.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = "c6cbfc534fad"
+down_revision: Union[str, None] = "c982a3fc4bf1"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Set status='complimentary' and plan='pro' for all existing accounts that
+    don't have a canceled or past_due subscription. Pilot users transition to
+    permanent complimentary Pro per spec section 5.
+
+    Forward-only — does not preserve original status values."""
+    conn = op.get_bind()
+    # Update existing rows
+    conn.execute(sa.text("""
+        UPDATE subscriptions
+        SET status = 'complimentary', plan = 'pro',
+            current_period_end = NULL, current_period_start = NULL,
+            updated_at = now()
+        WHERE status NOT IN ('canceled', 'past_due')
+    """))
+    # Backfill: any account without a Subscription row gets one
+    conn.execute(sa.text("""
+        INSERT INTO subscriptions (id, account_id, plan, status, cancel_at_period_end, created_at, updated_at)
+        SELECT gen_random_uuid(), a.id, 'pro', 'complimentary', false, now(), now()
+        FROM accounts a
+        WHERE NOT EXISTS (SELECT 1 FROM subscriptions s WHERE s.account_id = a.id)
+    """))
+
+
+def downgrade() -> None:
+    raise RuntimeError(
+        "Cannot downgrade: original subscription state is not preserved. "
+        "Restore from backup if needed."
+    )