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/server/src/routes/tariffs.ts

@@ -1,9 +1,12 @@
 import { randomUUID } from "node:crypto";
 import type { FastifyInstance } from "fastify";
-import { desc, eq, tariffVersions, tariffs, type Db } from "@parking/db";
-import { validateTariffStructure, type TariffStructure } from "@parking/shared";
+import { desc, eq, siteConfig, tariffVersions, tariffs, type Db } from "@parking/db";
+import { isTariffV2, validateTariffStructure, type TariffStructure } from "@parking/shared";
 import { requireRole } from "../auth.js";
 
+/** Default site timezone for wall-clock tariff windows when none is configured. */
+const DEFAULT_TZ = "Europe/Tirane";
+
 // Tariff composer API — the admin builds + edits the rate card at runtime. Tariffs
 // are EFFECTIVE-DATED IMMUTABLE VERSIONS: editing publishes a new version, never
 // mutates one; a session reprices against the version in force at its entry, and
@@ -58,7 +61,17 @@ export async function tariffRoutes(app: FastifyInstance, db: Db): Promise<void>
       if (!currency || typeof currency !== "string" || currency.length < 3) {
         return reply.code(400).send({ error: "currency (ISO 4217) required" });
       }
-      const problems = validateTariffStructure(structure);
+      // For a windowed (V2) structure, stamp the wall-clock timezone from SITE config
+      // (not the client) BEFORE validating — so the frozen tz is authoritative and the
+      // validation that requires tz passes. A V1 (bare) structure is left untouched.
+      let toStore: TariffStructure = structure;
+      if (structure && isTariffV2(structure)) {
+        const cfg = db.select().from(siteConfig).where(eq(siteConfig.id, 1)).get();
+        const tz = cfg?.timezone && cfg.timezone.length > 0 ? cfg.timezone : DEFAULT_TZ;
+        toStore = { ...structure, tz };
+      }
+
+      const problems = validateTariffStructure(toStore);
       if (problems.length) {
         return reply.code(400).send({ error: "invalid tariff structure", problems });
       }
@@ -94,7 +107,7 @@ export async function tariffRoutes(app: FastifyInstance, db: Db): Promise<void>
         tariffId,
         effectiveFrom: effective,
         currency,
-        structure: structure as unknown as Record<string, unknown>,
+        structure: toStore as unknown as Record<string, unknown>,
         createdBy: req.user?.username ?? null,
       };
       db.insert(tariffVersions).values(row).run();