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

packages/db/drizzle/0004_subscriptions_rename.sql

@@ -0,0 +1,25 @@
+-- Rename permit → subscription (master data only). The signed ledger keeps its
+-- immutable `permitId` payload — NOT touched here. Data-preserving ALTER RENAMEs
+-- (SQLite 3.25+) rather than drop/recreate, so existing subscriptions survive.
+-- Adds per-subscription pricing (price_minor + period + currency) and a site-wide
+-- default monthly price. See wiki/entities/subscription.md.
+
+ALTER TABLE `permits` RENAME TO `subscriptions`;
+--> statement-breakpoint
+ALTER TABLE `permit_credentials` RENAME TO `subscription_credentials`;
+--> statement-breakpoint
+ALTER TABLE `subscription_credentials` RENAME COLUMN `permit_id` TO `subscription_id`;
+--> statement-breakpoint
+ALTER TABLE `permit_plates` RENAME TO `subscription_plates`;
+--> statement-breakpoint
+ALTER TABLE `subscription_plates` RENAME COLUMN `permit_id` TO `subscription_id`;
+--> statement-breakpoint
+ALTER TABLE `subscriptions` ADD `price_minor` integer;
+--> statement-breakpoint
+ALTER TABLE `subscriptions` ADD `period` text DEFAULT 'monthly' NOT NULL;
+--> statement-breakpoint
+ALTER TABLE `subscriptions` ADD `currency` text;
+--> statement-breakpoint
+ALTER TABLE `sessions` RENAME COLUMN `permit_id` TO `subscription_id`;
+--> statement-breakpoint
+ALTER TABLE `site_config` ADD `subscription_monthly_price_minor` integer;