fix(billing): pending_checkouts ON DELETE CASCADE (mig 069) — unblock team reap (#272)

053_pending_checkouts created the team_id FK without ON DELETE CASCADE — the ONLY
team-child table missing it. DeleteTeamHard (the e2e-account reap) and the worker
team_deletion_executor delete a team with a bare DELETE FROM teams and rely on
children cascading, so a team that ever started a checkout (→ a pending_checkouts
row) failed:
  pq: ... violates foreign key constraint "pending_checkouts_team_id_fkey"

This surfaced live the moment test-cohort checkout was armed: a cohort Pro upgrade
creates a pending_checkouts row, so the reap 503'd (db_failed) and the cohort team
LEAKED — breaking the rule-24 'cohort data is always reaped' guarantee. Found by
the real test-card payment run.

Migration 069 aligns the FK with every other team-child table (ON DELETE CASCADE),
idempotent (DROP IF EXISTS + re-ADD). Already applied live; this codifies it.

Test: TestDeleteTeamHard_CascadesPendingCheckouts seeds a pending_checkouts row
and asserts DeleteTeamHard cascades it instead of erroring.

Co-authored-by: Claude <noreply@anthropic.com>

Author: mastermanas805

internal/db/migrations/069_pending_checkouts_cascade.sql

@@ -0,0 +1,28 @@
+-- 069_pending_checkouts_cascade — make pending_checkouts.team_id cascade on team delete.
+--
+-- WHY THIS EXISTS
+-- ---------------
+-- 053_pending_checkouts created the FK as `team_id UUID NOT NULL REFERENCES
+-- teams(id)` with NO `ON DELETE CASCADE` — the ONLY team-child table that omits
+-- it (every other child: deployments, stacks, api_keys, audit_log, vault,
+-- custom_domains, pending_deletions, pending_propagations, … all CASCADE).
+--
+-- DeleteTeamHard (the e2e-account reap) and the worker team_deletion_executor
+-- both delete a team with a single `DELETE FROM teams`, relying on the children
+-- to cascade. A team that ever started a checkout has a pending_checkouts row,
+-- so the delete fails:
+--   pq: update or delete on table "teams" violates foreign key constraint
+--   "pending_checkouts_team_id_fkey" on table "pending_checkouts"
+-- This surfaced the moment test-cohort checkout was armed (a cohort upgrade
+-- creates a pending_checkouts row) — the reap 503'd and the cohort team leaked,
+-- breaking the rule-24 "cohort data is always reaped" guarantee.
+--
+-- Fix: align the FK with every other team-child table — ON DELETE CASCADE. A
+-- resolved or unresolved pending_checkouts row is per-team bookkeeping; when the
+-- team is gone the row is meaningless, so cascading the delete is correct.
+-- Idempotent (DROP IF EXISTS + re-ADD) so it is safe to re-run.
+
+ALTER TABLE pending_checkouts DROP CONSTRAINT IF EXISTS pending_checkouts_team_id_fkey;
+ALTER TABLE pending_checkouts
+  ADD CONSTRAINT pending_checkouts_team_id_fkey
+  FOREIGN KEY (team_id) REFERENCES teams(id) ON DELETE CASCADE;

internal/models/e2e_account_models_test.go

@@ -77,6 +77,42 @@ func TestDeleteTeamHard_DeletesAndIsIdempotent(t *testing.T) {
 	require.False(t, deleted, "re-delete of a gone team is a clean no-op")
 }
 
+// TestDeleteTeamHard_CascadesPendingCheckouts is the regression guard for
+// migration 069: a team that started a checkout has a pending_checkouts row, and
+// before 069 that FK had no ON DELETE CASCADE — so DeleteTeamHard (the e2e reap)
+// failed with `pending_checkouts_team_id_fkey` and the cohort team LEAKED. This
+// surfaced the instant test-cohort checkout was armed (a cohort Pro upgrade
+// creates a pending_checkouts row → the reap 503'd). With the cascade, deleting
+// the team removes its pending_checkouts rows and the reap succeeds.
+func TestDeleteTeamHard_CascadesPendingCheckouts(t *testing.T) {
+	skipUnlessE2EModelsDB(t)
+	ctx := context.Background()
+	db, clean := testhelpers.SetupTestDB(t)
+	defer clean()
+
+	team, err := models.CreateTestCohortTeam(ctx, db, "cohort-with-checkout")
+	require.NoError(t, err)
+
+	// Seed a pending_checkouts row (the exact FK that used to block the delete).
+	subID := "sub_test_" + uuid.NewString()
+	_, err = db.ExecContext(ctx,
+		`INSERT INTO pending_checkouts (subscription_id, team_id, customer_email, plan_tier)
+		 VALUES ($1, $2, $3, $4)`,
+		subID, team.ID, "cohort@example.com", "pro")
+	require.NoError(t, err, "seed pending_checkouts")
+
+	// Pre-069 this returned the FK-violation error; with the cascade it succeeds.
+	deleted, err := models.DeleteTeamHard(ctx, db, team.ID)
+	require.NoError(t, err, "DeleteTeamHard must cascade pending_checkouts, not error on the FK")
+	require.True(t, deleted)
+
+	// The child row is gone too (cascaded), not orphaned.
+	var n int
+	require.NoError(t, db.QueryRowContext(ctx,
+		`SELECT count(*) FROM pending_checkouts WHERE subscription_id = $1`, subID).Scan(&n))
+	require.Equal(t, 0, n, "pending_checkouts row must be cascade-deleted with the team")
+}
+
 func TestMarkTeamResourcesForReaper_RetiersAndExpires(t *testing.T) {
 	skipUnlessE2EModelsDB(t)
 	ctx := context.Background()