fix(session): use state-enriched bill on give restart to preserve rendezvous

The restart closure in showBill() captured the original bill parameter
which has no nonce. On restart, a fresh nonce was generated producing a
different rendezvous key — so device 2 could never grab the bill.

Read the current bill from BillController state instead, which carries
the nonce from the first presentation.

Author: bmc08gt

apps/flipcash/shared/session/src/main/kotlin/com/flipcash/app/session/internal/RealSessionController.kt

@@ -334,7 +334,11 @@ class RealSessionController @Inject constructor(
                                                     message = "Cash link not sent. Restarting awaiting grab",
                                                     type = TraceType.User,
                                                 )
-                                                awaitBillGrab(bill, owner)
+                                                // Use the state-enriched bill which carries the
+                                                // nonce from the first presentation, so the
+                                                // restarted give reuses the same rendezvous.
+                                                val currentBill = billController.state.value.bill ?: bill
+                                                awaitBillGrab(currentBill, owner)
                                             }
                                         }
                                     ),