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

packages/devices/src/interfaces.ts

@@ -209,12 +209,28 @@ export interface TicketData {
   readonly header?: TicketHeader;
 }
 
+/** A subscription card: the customer's keepsake, printed at the booth on creation
+ *  (and re-printable). The driver renders the `code` as a SCANNABLE QR (the
+ *  subscriber scans it every entry/exit) plus the code as text + the holder/validity.
+ *  See wiki/entities/subscription.md. */
+export interface SubscriptionCardData {
+  /** The credential value to encode in the QR (e.g. "SUB-…"). */
+  readonly code: string;
+  readonly holderName?: string | null;
+  /** Coverage window, for the printed card (human-readable already, or ISO). */
+  readonly validFrom?: string | null;
+  readonly validTo?: string | null;
+  readonly header?: TicketHeader;
+}
+
 export interface PrinterDevice extends Device {
   printTicket(data: TicketData): Promise<void>;
   /** Print a free-form text report (a shift Z-report, a receipt). `lines` are
    *  printed as-is; the driver adds a header/cut. Kept generic so the business
    *  layer composes the content. See wiki/concepts/shift.md. */
   printReport(report: PrintReport): Promise<void>;
+  /** Print a subscription card: a scannable QR of the code + holder/validity. */
+  printSubscriptionCard(data: SubscriptionCardData): Promise<void>;
 }
 
 export interface PrintReport {