feat(fusion_accounting_followup): per-partner state migration from Enterprise

Migrates Enterprise account_followup per-partner state to Fusion fields:
- res.partner.followup_status -> fusion_followup_status (action_due/no_action)
- res.partner.payment_next_action_date -> fusion_followup_paused_until
  (when future-dated; sets status to 'paused')
- res.partner.followup_line_id -> fusion_followup_last_level_id
  (resolved by name match against migrated levels)

Wired into fusion.migration.wizard.action_run_migration after the
existing _followup_bootstrap_step. Idempotent: skips partners whose
Fusion state is already non-default. Defensive against missing
Enterprise fields (each field probed individually before use).

Closes the per-partner state migration gap that was blocking
Enterprise account_followup uninstall.

Made-with: Cursor

fusion_accounting_followup/tests/test_migration_round_trip.py

@@ -19,3 +19,12 @@ class TestFollowupMigrationRoundTrip(TransactionCase):
         # Second run skips what first created (or both no-op)
         if first['enterprise_module_present']:
             self.assertGreaterEqual(second['skipped'], first['created'])
+
+    def test_partner_state_bootstrap_step(self):
+        """Verify the partner-state migration step runs without error."""
+        wizard = self.env['fusion.migration.wizard'].create({})
+        result = wizard._followup_partner_state_bootstrap_step()
+        self.assertEqual(result['step'], 'followup_partner_state')
+        self.assertIn(result['enterprise_module_present'], [True, False])
+        self.assertGreaterEqual(result['updated'], 0)
+        self.assertGreaterEqual(result['skipped'], 0)