feat(tariff): V2 — legacy-parity pricing (time-of-day, category, seasonal, flat)

Bring the legacy ParkSQL2017 pricing BREADTH onto our engine while keeping
integer-minor-unit money + immutable signed versions (rejecting legacy's
float money / mutable rows). TariffStructure becomes a discriminated union:
V1 = the original bare ladder (UNCHANGED, verbatim algorithm, golden-
regression-tested against the live version); V2 = {version:2, tz, shared
knobs, defaultCard, windowedCards[]} where each card is flat OR a block
ladder and may be scoped by wall-clock hour window / day-of-week / date
range / vehicle category.

computeFeeV2 prices by stepping one increment at a time, advancing the
ladder by ELAPSED minutes (continuous) while selecting the active card by
WALL-CLOCK time in the version's FROZEN tz. Decisions: tz is a per-site
setting (site_config.timezone, default Europe/Tirane) stamped server-side
into each version on publish — never the host clock (reproducibility);
default-card cap governs a mixed day; precedence = specificity
(date>dow>hour) -> priority -> name (total, order-independent), validation
rejects ambiguous ties; category = a card FIELD, frozen in the signed
vehicle_entry payload (site_config.default_vehicle_category default), read
at both pricing call-sites.

Composer: default card front-and-centre (flat/ladder toggle), tiers under
an "Advanced" disclosure; emits BARE V1 when no tiers (back-compat). DB:
migrations 0005 (timezone) + 0006 (default_vehicle_category). Stood up
vitest in @parking/shared (was zero tests on the ledger-feeding fee fn);
36 tests incl. golden V1 regression, happy-hour/overnight/dow/flat/category/
cap edges, precedence shuffle-invariance, Europe/Tirane DST determinism,
validation matrix — all green. No event-chain change.

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

apps/web/src/api.ts

@@ -240,7 +240,10 @@ export interface TariffBlock {
   uptoMin: number | null;
   priceMinorPerIncrement: number;
 }
-export interface TariffStructure {
+// Mirrors @parking/shared. Two shapes: V1 (bare ladder) and V2 (default + windowed
+// cards by time-of-day / dow / date / category, flat or laddered). The discriminant
+// is the presence of `defaultCard`. See wiki/concepts/tariff-time-tiers.md.
+export interface TariffStructureV1 {
   gracePeriodEntryMin: number;
   incrementMin: number;
   blocks: TariffBlock[];
@@ -249,6 +252,39 @@ export interface TariffStructure {
   gracePeriodExitMin: number;
   overstay: "reprice";
 }
+export interface TariffWindow {
+  dow?: number[];
+  dateFrom?: string;
+  dateTo?: string;
+  fromHour?: string;
+  toHour?: string;
+}
+export interface TariffCard {
+  name: string;
+  priority: number;
+  category?: string;
+  window?: TariffWindow;
+  flatMinor?: number;
+  blocks?: TariffBlock[];
+  dailyCapMinor?: number | null;
+}
+export interface TariffStructureV2 {
+  version: 2;
+  tz: string;
+  gracePeriodEntryMin: number;
+  incrementMin: number;
+  lostTicketMinor: number;
+  gracePeriodExitMin: number;
+  overstay: "reprice";
+  defaultCard: TariffCard;
+  windowedCards?: TariffCard[];
+}
+export type TariffStructure = TariffStructureV1 | TariffStructureV2;
+
+/** True when a structure is the windowed V2 shape (mirrors @parking/shared isTariffV2). */
+export function isTariffV2(t: TariffStructure): t is TariffStructureV2 {
+  return (t as TariffStructureV2).defaultCard != null;
+}
 export interface TariffVersion {
   id: string;
   tariffId: string;
@@ -446,6 +482,11 @@ export interface SiteConfig {
   address: string | null;
   phone: string | null;
   email: string | null;
+  /** IANA timezone for tariff wall-clock windows (e.g. "Europe/Tirane"). Copied into
+   *  each published tariff version so its windows are frozen. */
+  timezone: string | null;
+  /** Default vehicle/customer category frozen onto each transient entry (V2 pricing). */
+  defaultVehicleCategory: string | null;
 }
 
 export function fetchOccupancy(): Promise<Occupancy> {