feat(billing): show subscription quota usage in admin usage records

Surface billing_source from h5_usage_records so plan-covered consumption
displays as 套餐额度 instead of missing from the usage tab.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/pagination.mjs

@@ -156,7 +156,7 @@ export async function listUsagePaged(pool, query) {
   );
   const [rows] = await pool.query(
     `SELECT r.id, r.user_id, u.username, u.display_name, r.agent_session_id, r.request_id,
-            r.input_tokens, r.output_tokens, r.cost_cents, r.balance_after_cents, r.created_at
+            r.input_tokens, r.output_tokens, r.cost_cents, r.balance_after_cents, r.billing_source, r.created_at
      FROM h5_usage_records r
      JOIN h5_users u ON u.id = r.user_id
      ${where}
@@ -176,6 +176,7 @@ export async function listUsagePaged(pool, query) {
       outputTokens: Number(row.output_tokens),
       costCents: Number(row.cost_cents),
       balanceAfterCents: Number(row.balance_after_cents),
+      billingSource: row.billing_source ?? 'wallet',
       createdAt: Number(row.created_at),
     })),
     total: Number(total),