feat(admin): redesign withdrawal review page and drop dead withdrawal code

- Split PayWithdrawals into shell + PayWithdrawalsList flat sibling trait
- Add process/policy callout, open/paid/fee stats, status views with counts
- Filter by source and payout method; reset keeps the status view
- Show net payout with gross/fee breakdown, copyable payee, note column
- Replace inline select form with per-row actions and a confirm dialog;
  reject requires a reason; double-submit guard; retry reuses the
  idempotency key; redirect back preserving filters and paging
- Withdrawal: add get_status_counts() and method filter; get_stats() now
  returns open_gross / paid_net / paid_fee
- Remove unused REST routes (/payment/withdrawals, /transition),
  admin_withdrawals(), update_status(), has_open_withdrawal(),
  count_open(), resolve_gross_amount()

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/widget-system/financial-flow-contract.test.cjs

@@ -59,8 +59,9 @@ test('orders have no independent flow page or visible flow number', () => {
   assert.equal(fs.existsSync(path.join(root, 'src/Finance/FinancialFlowQuery.php')), false)
   assert.match(payOrders, /订单明细/)
   assert.doesNotMatch(payOrders, /账本流水号|资金流水号/)
-  assert.match(read('src/Admin/Native/PayWithdrawals.php'), /esc_html__\('订单号'/)
-  assert.doesNotMatch(read('src/Admin/Native/PayWithdrawals.php'), /esc_html__\('流水号'|提现单号/)
+  const withdrawals = ['PayWithdrawals', 'PayWithdrawalsList'].map((f) => read(`src/Admin/Native/${f}.php`)).join('\n')
+  assert.match(withdrawals, /esc_html__\('订单号'/)
+  assert.doesNotMatch(withdrawals, /esc_html__\('流水号'|提现单号/)
   // 前台订单详情只展示公开订单号，账本流水号不下发也不展示。
   assert.match(read('assets/js/order-center.js'), /\["订单号", order\.order_number\]/)
   assert.doesNotMatch(read('assets/js/order-center.js'), /flow_number|账本流水号/)