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

wiki/index.md

@@ -80,7 +80,7 @@ Counts: 4 sources · 19 entities · 42 concepts · 5 decision records.
 ## Concepts — business domain
 - [[parking-session]] — the core domain entity; a projection over the signed log, never a mutable table.
 - [[tariff]] — fee model; pure, data-driven, offline; pay-on-foot adds a walk-back grace window.
-- [[tariff-time-tiers]] — design: happy-hour/off-peak/weekend/seasonal + vehicle categories via time-windowed rate cards.
+- [[tariff-time-tiers]] — BUILT (V2 tariff): happy-hour/off-peak/weekend/seasonal + vehicle category + flat rate via wall-clock windowed cards; tz frozen per version.
 - [[booth-exit-flow]] — manned booth: pay → voucher (self-exit later) or immediate exit; active sessions; audited barrier re-open.
 - [[shift]] — manned-only accountability period; explicit Start/End; End → signed + printed Z-report; drawer float carries across shifts.
 - [[capacity-occupancy]] — live count = open sessions; refuse entry + FULL sign when full (soft policy); exit never blocked.