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

wiki/concepts/tariff.md

@@ -20,6 +20,12 @@ beyond the host).
 > reproducible repricing. The operator selects a plan + span; the price is looked up, never typed.
 > Tariffs price *transient* stays by duration; plans price *subscription* spans by ceil(periods).
 
+> **The tariff also prices SUBSCRIBERS now (2026-06-20).** A [[subscription]] plan with time windows
+> charges the **transient tariff** for any out-of-window parking (early entry / late exit) — the
+> subscriber temporarily *becomes* a transient for those minutes. `computeFee` is reused unchanged;
+> the gap is a normal `[start, end]` priced against the active version (recorded `tariffVersionId` for
+> reproducibility). See [[subscription]] "the tariff bridge".
+
 > Decisions (2026-06-15): (1) tariffs are **effective-dated, immutable versions** — editing
 > publishes a new version, never mutates an old one; (2) **one active tariff per site** (versioned
 > over time), modelled with an id/scope so multiple rate cards can be added later without migration;