feat: subscription v2 — quantity pricing, plan timeframes (tariff bridge), reserved spots

Three subscriber enhancements driven by real scenarios (migration 0011, all
additive columns — backward-compatible).

1. QUANTITY. One subscription covers N cars (a family pays once for two). Sale
   amount = span price × quantity; maxConcurrent defaults to the quantity so all
   N cars can be inside. Quantity rides in the payment payload.

2. PLAN TIMEFRAMES → TARIFF BRIDGE. A plan may restrict WHEN a subscriber may
   park (e.g. weekday 20:00→08:00, weekend all-day). A scan outside the window is
   NOT refused — the out-of-window minutes are charged at the normal TRANSIENT
   tariff (the subscriber is a transient for that time):
     - early entry: arrival → window-open, DEFERRED (signed as windowOwedMinor on
       the vehicle_entry payload), collected at exit;
     - late exit: window-close → departure, and exit is GATED
       (sub.refused.unpaidWindow) until paid at the booth.
   Pure, tz-aware outOfWindowGap in @parking/shared (12 unit tests); pricing
   reuses computeFee + the active tariff version
   (apps/server/src/subscription-window.ts). The exit refusal is a host-ONLINE
   business gate — the fail-open rule still governs the offline path.

3. RESERVED SPOTS. Site toggle reserve_subscriber_spots: occupancy holds
   max(0, quantity − itsCarsInside) per active subscription, so transients see
   "full" sooner; effectiveFree = capacity − count − reserved. Subscribers are
   never gated by full.

UI: quantity field + ×N quote (SubscriptionManager); timeframes editor
(SubscriptionPlansManager); reserve checkbox (SiteSettings); booth pay modal
shows an "OUT-OF-WINDOW" charge and takes payment to clear the exit gate.

Verified on a copy of the live DB: qty 2 = 2× price; a night-plan 19:30 entry →
30min/15,000 ALL owed, stamped + paid → gate clears, chain verifies; the reserve
toggle holds a qty-2 sub's 2 spots. Build+lint 12/12; 80 shared tests pass.

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

apps/web/src/SiteSettings.tsx

@@ -25,6 +25,7 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
   const [capInput, setCapInput] = useState("");
   const [meta, setMeta] = useState<Record<string, string>>({});
   const [exitVoucherDefault, setExitVoucherDefault] = useState(false);
+  const [reserveSubs, setReserveSubs] = useState(false);
   const [msg, setMsg] = useState<string | null>(null);
 
   function reload() {
@@ -36,6 +37,7 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
       .then((c) => {
         setCapInput(c.capacity == null ? "" : String(c.capacity));
         setExitVoucherDefault(c.exitVoucherDefault);
+        setReserveSubs(c.reserveSubscriberSpots);
         const m: Record<string, string> = {};
         for (const { key } of META_FIELDS) m[key] = c[key] == null ? "" : String(c[key]);
         setMeta(m);
@@ -49,6 +51,7 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
     const patch: Partial<SiteConfig> = {
       capacity: raw === "" ? null : Math.round(Number(raw)),
       exitVoucherDefault,
+      reserveSubscriberSpots: reserveSubs,
     };
     // Send each metadata field; "" → null is applied server-side.
     for (const { key } of META_FIELDS) (patch as Record<string, string | null>)[key] = meta[key] ?? "";
@@ -97,6 +100,18 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
             {t("site.printExitDefault")}
             <span className="hint">{t("site.printExitHint")}</span>
           </label>
+          <label className="flex items-start gap-2 text-[12px] text-term-text">
+            <input
+              type="checkbox"
+              className="mt-0.5 accent-term-amber"
+              checked={reserveSubs}
+              onChange={(e) => setReserveSubs(e.target.checked)}
+            />
+            <span>
+              {t("site.reserveSubs")}
+              <span className="hint block">{t("site.reserveSubsHint")}</span>
+            </span>
+          </label>
           <div className="border-t border-term-border pt-3 text-[11px] uppercase tracking-wider text-term-muted">
             {t("site.parkDetails")}
           </div>