fix(i18n): backfill 120 missing keys + close 2 typo regressions from purchase refactor

Surface: users (and especially Серёжа в bugs topic) were seeing raw i18n keys
like `subscription.promoGroup.title` rendered as literal text on the renewal
screen. Audit found 118 keys referenced in code that were absent from all 4
locale files, plus 140 keys missing only in zh/fa (silently falling back to
Russian for those users).

Root causes:
- cf52999 (extract TariffPickerGrid) introduced `subscription.promoGroup.title`
  that never existed — should have been `subscription.promoGroup.yourGroup`.
- Subscription.tsx used `subscription.autopay.title` (object path) while
  SubscriptionListCard.tsx used `subscription.autopay` (leaf) — i18next can't
  hold both shapes for the same key.
- Many user-flow keys (subscription.notFound, subscriptions.empty, common.ok,
  successNotification.*, etc.) were never added when their components landed.
- Historical drift had ~140 keys in ru/en that never got zh/fa translations.

Fix:
- Rename TariffPickerGrid usage `promoGroup.title` → `promoGroup.yourGroup`.
- Rename Subscription.tsx usage `autopay.title` → `autopay`.
- Add 116 brand-new keys across ru/en/zh/fa (464 entries).
- Add 8 partially-missing keys (en+ru gaps) for landing periods, dashboard
  campaign/referrer stats, and promo offer failure counts.
- Translate 280 entries to close the zh/fa drift.

Final state: 0 keys missing in any of the 4 locale files for any code-referenced
translation key. Build + tsc green.

src/pages/Subscription.tsx

@@ -1086,7 +1086,7 @@ export default function Subscription() {
                     disabled={autopayMutation.isPending}
                     role="switch"
                     aria-checked={subscription.autopay_enabled}
-                    aria-label={t('subscription.autopay.title', 'Auto-payment')}
+                    aria-label={t('subscription.autopay', 'Auto-payment')}
                     className="relative h-7 w-[52px] rounded-full transition-colors duration-300"
                     style={{
                       background: subscription.autopay_enabled ? zone.mainHex : g.textGhost,