feat(subscription): QR credentials — operator-choose (QR-only now), auto-generate, multi-month, printed card

Builds out subscription credentials on top of the rename.

- Operator chooses the credential type; only QR is live (RFID shown disabled
  "soon"). Backend/schema keep accepting both — re-enabling RFID is UI-only.
- QR codes are AUTO-GENERATED server-side (SUB-<base32>, crypto-random,
  globally-unique-checked) — the customer/operator never picks the value.
  RF stays operator-entered (the physical card id). Reader output decided =
  TCP/IP full string (Wiegand-numeric fallback noted).
- Multi-month: form takes a `months` count → server sets validTo =
  validFrom + N months (day-clamp); one record/one window; total = N×monthly.
- The QR card is PRINTED so the operator can hand it over: real ESC/POS 2D QR
  (GS ( k) added to the Rongta driver (printSubscriptionCard); auto-print on
  create (best-effort — never fails the create; returns {printed,printError})
  + reprint via POST /api/subscriptions/:id/print and a "Print code" button.

Verified via buildServer+inject incl. a TCP capture of the on-wire QR bytes
(autogen+uniqueness, Jan31+3mo→Apr30, auto-print, GS ( k QR with embedded
code, reprint, no-QR→409). Updated wiki (subscription, rongta-printer). No
migration.

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

apps/web/src/lib/i18n/en.ts

@@ -144,18 +144,30 @@ export const en: Catalog = {
     limitCarsInAtOnce: "limit cars in at once",
     validFrom: "Valid from",
     validTo: "Valid to",
+    months: "Months",
+    monthsHint: "months paid",
+    coverageHint: "until {{end}}",
+    totalDue: "total {{total}}",
+    validToOverride: "Valid to (manual)",
     isoDateOptional: "ISO date (optional)",
     boundPlates: "Bound plates",
     commaSeparatedOptional: "comma-separated (optional)",
+    credentials: "Credentials",
     credentialsCardQr: "Credentials (card / QR)",
     rfCardTag: "RF card/tag",
+    rfCardTagSoon: "RF card/tag (soon)",
     qr: "QR",
+    qrAutoGen: "QR code is auto-generated on save",
     credentialValue: "credential value",
     addCredential: "+ credential",
     needCredentialOrPlate: "A subscription needs at least one credential OR one bound plate.",
     save: "Save",
     cancel: "Cancel",
     saved: "Subscription saved.",
+    savedPrinted: "Subscription saved — QR code printed.",
+    savedPrintFailed: "Subscription saved, but printing failed ({{error}}). Use \"Print code\".",
+    printCode: "Print code",
+    printedOn: "Code printed on {{printer}}.",
     confirmRevoke: "Revoke subscription for {{name}}? It will be refused at the barrier.",
     confirmDelete: "Delete subscription for {{name}}? (Past events are kept.)",
     statusActive: "active",