feat(machine): open a verified Bolt Card session at tap-to-enter

Entry now spends the tap's single-use SUN once, on the card server's new
/session endpoint (aiolabs/boltcards feat/card-session-endpoint), instead
of parsing the lnurlw locally and deferring every check to Complete. The
server proves a genuine, non-replayed card and returns the wallet balance
plus the hit-keyed LUD-03 withdraw and LUD-06 pay second steps — the same
single-use bearer /scan and /pay hand out — so Complete still needs no
second tap and the ATM holds no p/c for the visit.

- electron/boltcard-session.ts: /scan → /session URL derivation, response
  parsing, 404 → 'card server does not support sessions'.
- lnurl-withdraw / lnurl-pay: the second steps are now callable on their
  own (executeWithdrawCallback, resolveInvoiceFromPayStep); the tap paths
  are unchanged and reuse them.
- IPC: lnurl:open-card-session, lnurl:withdraw-session, lnurl:pay-session.
- store: handleBoltCardEntry opens the session then authorizes the
  server-returned external_id; the payment handlers take a source (raw
  tap or session); a withheld withdraw step declines with the server's
  reason. The boltcard AccessScan no longer carries the lnurlw.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

apps/machine/electron/preload.ts

@@ -141,6 +141,23 @@ contextBridge.exposeInMainWorld('electronAPI', {
   }): Promise<{ ok: boolean; bolt11?: string; reason?: string }> =>
     ipcRenderer.invoke('lnurl:pay-card', args),
 
+  // Bolt Card tap-to-enter: one verified session per tap (balance + fiat +
+  // the withdraw/pay second steps reused at Complete). Payload shapes are
+  // declared in src/types/electron.d.ts (CardSession).
+  openCardSession: (args: { lnurlw: string }): Promise<unknown> =>
+    ipcRenderer.invoke('lnurl:open-card-session', args),
+  withdrawWithSession: (args: {
+    withdraw: { callback: string; k1: string; minWithdrawable?: number; maxWithdrawable?: number }
+    bolt11: string
+    amountMsat?: number
+  }): Promise<{ ok: boolean; reason?: string }> =>
+    ipcRenderer.invoke('lnurl:withdraw-session', args),
+  resolveSessionInvoice: (args: {
+    pay: { callback: string; minSendable?: number; maxSendable?: number; metadata?: string }
+    amountMsat: number
+  }): Promise<{ ok: boolean; bolt11?: string; reason?: string }> =>
+    ipcRenderer.invoke('lnurl:pay-session', args),
+
   applyOperatorCassettesConfig: (
     payload: {
       positions: Record<string, { denomination: number; count: number }>