feat(admin): 计费页加「余额硬拦截」开关 + 各租户「充值」按钮

闭合积分环的配置/操作端，接到 P4 后端：
- 计费规则区：加「余额硬拦截」开关（credit_enforce），与汇率合成一个「保存规则」。
- 用量观测·租户排行：每行加「充值」按钮（正=充值、负=校正），调 /admin/credits/grant，
  充值后即时刷新余额。
- api：getBillingConfig/saveBillingConfig 带 credit_enforce；新增 grantCredits。

live 验证(preview)：开关渲染+可存；点公司A「充值 10」→余额 5.92→15.92、账本落对租户；
tsc + 41 vitest 全过。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-admin/src/components/BillingRules.tsx

@@ -18,9 +18,10 @@ interface Row {
 export function BillingRules({ onSaved }: { onSaved?: () => void }) {
   const [rows, setRows] = useState<Row[]>([]);
   const [rate, setRate] = useState(""); // tokens_per_credit
-  const [rateDirty, setRateDirty] = useState(false);
-  const [rateSaving, setRateSaving] = useState(false);
-  const [rateMsg, setRateMsg] = useState("");
+  const [enforce, setEnforce] = useState(false); // 硬拦截开关
+  const [cfgDirty, setCfgDirty] = useState(false);
+  const [cfgSaving, setCfgSaving] = useState(false);
+  const [cfgMsg, setCfgMsg] = useState("");
   const [loading, setLoading] = useState(true);
   const [err, setErr] = useState("");
 
@@ -45,7 +46,8 @@ export function BillingRules({ onSaved }: { onSaved?: () => void }) {
       };
       setRows([...chat.map(mk), ...emb.map(mk)]);
       setRate(String(cfg.tokens_per_credit));
-      setRateDirty(false);
+      setEnforce(cfg.credit_enforce);
+      setCfgDirty(false);
     } catch (e) {
       setErr((e as Error).message);
     } finally {
@@ -75,23 +77,23 @@ export function BillingRules({ onSaved }: { onSaved?: () => void }) {
     }
   };
 
-  const saveRate = async () => {
+  const saveConfig = async () => {
     const n = Number(rate);
     if (!(n > 0)) {
-      setRateMsg("汇率必须 > 0");
+      setCfgMsg("汇率必须 > 0");
       return;
     }
-    setRateSaving(true);
-    setRateMsg("");
+    setCfgSaving(true);
+    setCfgMsg("");
     try {
-      await saveBillingConfig(n);
-      setRateDirty(false);
-      setRateMsg("✓ 已保存");
+      await saveBillingConfig(n, enforce);
+      setCfgDirty(false);
+      setCfgMsg("✓ 已保存");
       onSaved?.();
     } catch (e) {
-      setRateMsg((e as Error).message);
+      setCfgMsg((e as Error).message);
     } finally {
-      setRateSaving(false);
+      setCfgSaving(false);
     }
   };
 
@@ -108,8 +110,8 @@ export function BillingRules({ onSaved }: { onSaved?: () => void }) {
         <span className="rounded bg-violet-50 px-2 py-0.5 text-[10px] font-medium text-violet-700">配置端</span>
       </div>
 
-      {/* 全局 token→积分 汇率 */}
-      <div className="mb-5 flex flex-wrap items-end gap-3 rounded-lg border border-violet-100 bg-violet-50/40 p-3">
+      {/* 全局：token→积分 汇率 + 硬拦截开关 */}
+      <div className="mb-5 flex flex-wrap items-end gap-5 rounded-lg border border-violet-100 bg-violet-50/40 p-3">
         <div>
           <label className="block text-[11px] font-medium text-gray-500">token → 积分 汇率</label>
           <div className="mt-1 flex items-center gap-2 text-sm text-gray-600">
@@ -120,22 +122,38 @@ export function BillingRules({ onSaved }: { onSaved?: () => void }) {
               value={rate}
               onChange={(e) => {
                 setRate(e.target.value);
-                setRateDirty(true);
-                setRateMsg("");
+                setCfgDirty(true);
+                setCfgMsg("");
               }}
               className="w-28 rounded border px-2 py-1 text-right font-mono text-xs focus:border-violet-500 focus:outline-none"
             />
             <span className="text-xs text-gray-400">token = 1 积分（设 1 即按 token 直计）</span>
           </div>
         </div>
+        <div>
+          <label className="block text-[11px] font-medium text-gray-500">余额硬拦截</label>
+          <label className="mt-1 flex cursor-pointer items-center gap-2 text-sm text-gray-600">
+            <input
+              type="checkbox"
+              checked={enforce}
+              onChange={(e) => {
+                setEnforce(e.target.checked);
+                setCfgDirty(true);
+                setCfgMsg("");
+              }}
+              className="h-4 w-4 accent-violet-600"
+            />
+            <span className="text-xs text-gray-400">开启后：租户积分余额 ≤0 拒绝新任务（默认关=软扣）</span>
+          </label>
+        </div>
         <button
-          onClick={() => void saveRate()}
-          disabled={!rateDirty || rateSaving}
+          onClick={() => void saveConfig()}
+          disabled={!cfgDirty || cfgSaving}
           className="rounded bg-violet-600 px-3 py-1 text-xs text-white hover:bg-violet-700 disabled:opacity-40"
         >
-          {rateSaving ? "保存中…" : "保存汇率"}
+          {cfgSaving ? "保存中…" : "保存规则"}
         </button>
-        {rateMsg && <span className={`text-[11px] ${rateMsg.startsWith("✓") ? "text-emerald-600" : "text-rose-600"}`}>{rateMsg}</span>}
+        {cfgMsg && <span className={`text-[11px] ${cfgMsg.startsWith("✓") ? "text-emerald-600" : "text-rose-600"}`}>{cfgMsg}</span>}
       </div>
 
       {/* 每模型单价 + 积分权重 */}