feat(subscription): rename permit→subscription + monthly pricing

The "permit/lejet" feature is really a subscription. Full rename of the
mutable master data, plus a recurring monthly price.

- DB (migration 0004, data-preserving ALTER RENAME): permits→subscriptions,
  permit_credentials/_plates→subscription_*, sessions.permit_id→subscription_id.
- Pricing: per-subscription priceMinor + period(monthly) + currency, with a
  site default (site_config.subscription_monthly_price_minor) pre-filling the form.
- Server: subscription-flow.ts (SubscriptionFlow), routes/subscriptions.ts
  (/api/subscriptions). Web: SubscriptionManager, route, i18n (sq Abonimet/en).
- The signed ledger `permitId` payload is intentionally kept — immutable
  hash-chained history; renaming it would break verification of past events.

Deferred (wiki notes): fee collection into the ledger/shift (a shift-attributed
payment), LPR/ANPR plate source, time-of-day access windows (overnight subscriber).

Also carries the device-footer UI surface (api DeviceStatus, router mount,
i18n devices) due to shared-file overlap with the preceding footer commit.

Verified end-to-end on a fresh DB and migration on a live-DB copy (sessions
preserved). Live DB migrated. Full monorepo builds clean.

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

wiki/concepts/reporting-analytics.md

@@ -17,7 +17,7 @@ derived and rebuildable, never a separate ledger.
 - **Revenue** — by day/week/shift, by tender (cash vs. card), gross vs. discounts vs. net. Source:
   `payment` events + [[validation-discounts|discount]] events + `shift_z_report` ([[shift]]).
 - **Occupancy** — current ([[capacity-occupancy]]) and historical curve; peak times; turnover.
-- **Stay analytics** — average/median duration, distribution; transient vs. [[permit]] split.
+- **Stay analytics** — average/median duration, distribution; transient vs. [[subscription]] split.
 - **Permit usage** — active permits, utilisation, concurrency vs. `maxConcurrent`.
 - **Anomalies** — out-of-band opens, never-exited sessions, occupancy drift, over-validation —
   the `anomaly` events + reconciliation findings ([[reconciliation]]).