feat(server-mode): spend quota per user — no new session, prompts refused once used up

An admin sets a default spend quota on the Users page and overrides it per
user (Edit user → Spend quota: default / no limit / their own), in dollars
per local day or per sliding 5 hours. Spend is the users page's own
hourlyTokenRows + calculateCost over the sessions a user owns.

Over the quota, until it opens again:
- spawnRun refuses every start/resume/home prompt with EQUOTA (429);
- a minute sweep writes each pane's AGENTHUB_QUOTA_FILE (host: data dir,
  member: handoff dir via write-as) and hook-handler.js exits 2 on
  UserPromptSubmit from that file alone (Claude Code, Codex with trusted
  hooks) — fail-open, never asks the dashboard, never for Antigravity;
- a member's omp on the shared login loses its gateway key (clientsFor);
- panes no hook can stop (Antigravity, Cursor, Codex without trusted
  hooks, omp on its own login) are ended.

GET /api/me/quota feeds a "Quota N%" chip in the status bar.
New: server/lib/user-quota.js, user_quotas table, PUT /api/users/quota-default,
PATCH /api/users/:id {quota}, docs in SERVER-MODE.md § Spend quotas.

client/src/components/StatusBar.tsx

@@ -22,6 +22,9 @@
  * its fullest window, live account only — and, on hover or focus, a panel
  * above grouping every account per tool (saved Claude profiles too): name,
  * sign-in expiry, and a row per window with its bar, percent and reset time.
+ * Server mode: the user's OWN spend quota (`GET /api/me/quota`, read with the
+ * costs) as "Quota N%" — amber from 80 %, red once used up, when the user can
+ * start nothing and their prompts are refused until it opens again.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -30,9 +33,9 @@ import { createPortal } from "react-dom";
 import { useTranslation } from "react-i18next";
 import { Link, useLocation } from "react-router-dom";
 import { RefreshCw, Wifi, WifiOff } from "lucide-react";
-import { api, type RunHandle } from "../lib/api";
+import { api, type RunHandle, type UserQuotaStatus } from "../lib/api";
 import type { BudgetStatus, CostResult, ToolQuota } from "../lib/types";
-import { fmt, fmtCostFull, formatModelName, timeAgo } from "../lib/format";
+import { fmt, fmtCostFull, formatDateTime, formatModelName, timeAgo } from "../lib/format";
 import { AiToolIcon } from "./AiToolIcon";
 import { useLiveRefresh } from "../hooks/useLiveRefresh";
 import { useSpin } from "../hooks/useSpin";
@@ -369,6 +372,8 @@ export function StatusBar({
   const [runs, setRuns] = useState<RunHandle[]>([]);
   // The budget furthest past one of its thresholds, if any.
   const [budget, setBudget] = useState<BudgetStatus | null>(null);
+  // Server mode: this user's own spend quota (null: none, or local mode).
+  const [myQuota, setMyQuota] = useState<UserQuotaStatus | null>(null);
   const location = useLocation();
   const shown = selectedFrom(location.pathname, location.search);
   const lane = shown.lane;
@@ -414,6 +419,10 @@ export function StatusBar({
         if (live()) setBudget(hit[0] ?? null);
       })
       .catch(() => undefined);
+    api.me
+      .quota()
+      .then((r) => live() && setMyQuota(r?.quota ?? null))
+      .catch(() => undefined);
     if (lane !== null) {
       api.pricing
         .totalCost({ lane })
@@ -524,6 +533,26 @@ export function StatusBar({
           {t("statusBar.budget", { pct: Math.round(budget.pct) })}
         </Link>
       )}
+      {myQuota && (
+        <span
+          data-testid="status-bar-user-quota"
+          title={t(myQuota.exceeded ? "statusBar.userQuotaBlocked" : "statusBar.userQuotaTitle", {
+            spend: usd(myQuota.spend),
+            limit: usd(myQuota.limit_usd),
+            period: t(`statusBar.userQuotaPeriod.${myQuota.period}`),
+            at: myQuota.resetsAt ? formatDateTime(myQuota.resetsAt) : "",
+          })}
+          className={`tabular-nums ${
+            myQuota.exceeded
+              ? "text-status-danger"
+              : myQuota.pct >= 80
+                ? "text-status-warning"
+                : "text-fg-muted"
+          }`}
+        >
+          {t("statusBar.userQuota", { pct: Math.min(999, Math.round(myQuota.pct)) })}
+        </span>
+      )}
       <QuotaChips />
     </footer>
   );