feat(tariff): complete the progressive ladder — require open-ended last block, hours-based composer

The stepped-block engine already does "first N hrs x X, next N hrs x Y, ...,
24h cap" (ordered blocks, per-block rate, rolling-24h cap). No new axis; this
completes the model and removes its footgun.

- validateTariffStructure (shared) now REQUIRES the last block to be open-ended
  (uptoMin: null). A bounded final block silently inherited its own rate past
  its bound (a hidden, never-stated price — e.g. the live ALL tariff billed
  hour 4+ at the 3rd-hour rate). rateAt() still prices legacy bounded-tail
  versions; validation is publish-only, so published immutable versions are
  unaffected (no migration).
- TariffComposer edits bands as a DURATION in hours ("first 2 hours, then next
  3 hours"), accumulated into the engine's cumulative uptoMin (minutes) on
  submit. The last row is a pinned, non-removable "thereafter (open-ended)"
  band, so a published card always satisfies the open-ended-last rule.
  blocksToForm round-trips stored minutes back to band hours (legacy loads).
- i18n: replaced upToMin/egExample with bandDuration/hoursUnit/egHours (sq+en,
  catalog parity green).

Verified: validator rejects bounded-last / accepts open-ended; computeFee
correct at 1/2/3/5/6/24h for a 0-2h@200,2-5h@100,5h+@50 + 1000 cap card. Full
build green. Wiki (tariff.md, log.md) updated.

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

wiki/log.md

@@ -844,3 +844,13 @@ Decoupled subscription exit from the entry credential. Previously the session wa
 ## [2026-06-18] fix | Subscription occurrences in the booth — prepaid, barrier-open assist (not transient)
 
 A subscription occurrence (SUBSESS-…) showed in Active Sessions but was wrongly treated as an unpaid transient: the modal tried to quote/charge it and the "open barrier" button only appeared for PAID sessions, so a subscriber with a faulty exit reader / missing card couldn't be assisted. Fix: `pay-station.ts` lookup/activeSessions now flag `subscription`/`subscriptionId`/`subscriptionHolder` from the entry payload (permit:true/permitId) and DON'T quote a subscription (amountMinor null). `exit-flow.ts` reopenBarrier now authorizes `paidAt != null || subscription` (prepaid). UI: the pay modal renders a SUBSCRIPTION mode (PREPAID badge, snapshots, single Open-barrier action, no tender/voucher) and the active row badges "abonim" + shows the holder name; both labelled by holder, not the raw key. Also SHORTENED the occurrence id (was SUBSESS-<subId>-<uuid>, ~80 chars) to `SUBSESS-<12hex>` — the subscriptionId lives in the payload (which every fold matches on), so it needn't be embedded in the key. Verified 9/9 (subscription flagged + not charged in lookup/active, reopen works without payment, unpaid-transient guard intact). Updated [[booth-exit-flow]]. No migration.
+
+## [2026-06-18] fix | Tariff versioning was retroactive — forbid backdated effectiveFrom
+
+The version selector picks "latest tariff_version with effectiveFrom ≤ session entry time" (correct intent: a past session reprices against the rate in force when it was incurred). But the publish handler (`routes/tariffs.ts`) accepted ANY `effectiveFrom` (defaulting to now). So an admin could publish a version with a **backdated** effectiveFrom and silently reprice sessions that had already entered — exactly the retroactive rewrite the versioning exists to prevent. Pricing itself was already sound: `quote()` resolves by `entry.occurredAt` and the `payment` event records `tariffVersionId`, so a COMPLETED session is frozen; the leak was entirely the publish side. Fix: reject `effectiveFrom` earlier than now (60 s skew tolerance); future-dated (scheduling a price change) stays allowed; bad ISO → 400. Decision (with user): forbid backdating + keep entry-time pinning; did NOT add tariffVersionId to vehicle_entry (entry-time selection + no-backdating already freezes the price). Together these make it structural: once a car has entered, no later publish can reprice it. Verified 5/5 via inject against a copy of the live DB (now→201, -1h→400, +1h→201, garbage→400, -10s skew→201). Updated [[tariff]]. No migration.
+
+## [2026-06-18] feat | Tariff: complete the progressive ladder — open-ended last block required + hours-based composer
+
+The owner asked for "first N hours × X, next N hours × Y, …, 24h cap" — which the stepped-block engine ALREADY does (ordered blocks, per-block rate, rolling-24h cap; computeFee tested). So no new axis: the work was making the model complete + footgun-free. Two changes. (1) **Forbid a bounded last block** — `validateTariffStructure` (shared) now rejects a final block with a non-null `uptoMin`, so the "thereafter" rate is always explicit; previously a bounded tail silently inherited its own rate past its bound (a hidden, never-stated price — e.g. the live ALL tariff's 180-min last block billed hour 4+ at the 3rd-hour rate). `rateAt()` still prices legacy bounded-tail versions gracefully and validation is publish-only, so immutable published versions are unaffected (no migration). (2) **Composer edits bands as a DURATION in hours**, not cumulative minutes — `BlockForm` carries `hours`; `toStructure` accumulates into cumulative `uptoMin` minutes; the last row is a pinned, non-removable, hours-less "thereafter (open-ended)" band; `blocksToForm` round-trips stored minutes back to band hours (legacy bounded tails still load). i18n: replaced `upToMin`/`egExample` with `bandDuration`/`hoursUnit`/`egHours` in sq+en (catalog parity green). Verified: validator rejects bounded-last / accepts open-ended; computeFee correct at 1/2/3/5/6/24h for a 0-2h@200,2-5h@100,5h+@50 + 1000 cap card. Full build green (shared/server/web). Updated [[tariff]]. No migration.
+
+NB considered-and-rejected: time-of-day / weekday wall-clock tiers ("timeframe") were offered but the owner explicitly chose the elapsed-duration ladder only — see [[tariff-time-tiers]] for the deferred wall-clock axis.