feat(drawer): drawer hub — balance now, this-shift figure, daily activity, shift history; busy spinners

/drawer was record + review only: no current balance, no sight of the open
shift's incomings, no daily activity, no shift history. Rebuilt as a hub:

- Drawer now: the till's running balance (new GET /api/drawer/balance,
  shift:read — exposes the service's existing drawerBalance(); the drawer
  is one site-wide till, same exposure the X-report already had) with the
  open shift's X-report breakdown alongside (float + takings + vouchers =
  expected = balance) and a "This shift: ±X" figure (expected − opening
  float — the shift's own contribution vs what it inherited).
- Today's cash activity: every cash payment + voucher since local
  midnight from the signed chain, live, with day totals (card never
  enters the till).
- Record + movements/review: the 2026-07-01 flow, unchanged.
- Closed shifts: drawer-focused history via the scope-aware /api/shifts
  (float → takings ± vouchers → expected per shift).

Also: every shift open/close button (header, /shifts, pay modal, end-
shift confirm) now shows an animated spinner + dims while busy — the old
label-swap-only feedback read as a dead click when a shift open ran slow.
The slowness itself (drawer/shift reads fold the WHOLE chain, O(chain))
is recorded as an open item in wiki/concepts/shift.md with the fix
sketch: fold from the last z-report's signed expectedDrawerMinor forward.

No new ledger surface — one read-only endpoint; RBAC test added.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/router.tsx

@@ -25,6 +25,7 @@ import {
 } from "./api.js";
 import { qk, queryClient } from "./lib/query.js";
 import { Modal } from "./ui/Modal.js";
+import { Spinner } from "./ui/Spinner.js";
 import { setLanguage } from "./lib/i18n/index.js";
 import { applyTheme, applyFontScale } from "./lib/theme.js";
 import { useLiveFeed } from "./lib/use-live-feed.js";
@@ -335,9 +336,15 @@ function ShiftButton() {
         disabled={busy || blockedByOther}
         title={blockedByOther ? t("shift.headerHeldBy", { operator: heldBy ?? "?" }) : undefined}
         onClick={onClick}
-        className={`rounded-term border px-2 py-0.5 text-[0.6875rem] font-semibold uppercase tracking-wider ${tone}`}
+        className={`rounded-term border px-2 py-0.5 text-[0.6875rem] font-semibold uppercase tracking-wider disabled:opacity-60 ${tone}`}
       >
-        {busy ? t("shift.opening") : label}
+        {busy ? (
+          <span className="inline-flex items-center gap-1.5">
+            <Spinner /> {isMine ? t("shift.ending") : t("shift.opening")}
+          </span>
+        ) : (
+          label
+        )}
       </button>
       {!isOpen && (
         <span className="text-[0.625rem] uppercase tracking-wider text-term-amber">{t("shift.headerNoShift")}</span>
@@ -409,7 +416,13 @@ function CloseShiftConfirm({
             {t("subs.cancel")}
           </button>
           <button type="button" className="btn btn-sm btn-danger" onClick={onConfirm} disabled={busy || !x}>
-            {busy ? t("shift.ending") : t("shift.endShift")}
+            {busy ? (
+              <span className="inline-flex items-center gap-1.5">
+                <Spinner /> {t("shift.ending")}
+              </span>
+            ) : (
+              t("shift.endShift")
+            )}
           </button>
         </div>
       </div>