feat: card rail via LNbits fiat providers (Stripe), per operator

A guest may pay a fiat-priced room by card when its owner has opted in and
LNbits core has a fiat provider for that user — resolved through
settings.get_fiat_providers_for_user(owner), the seam lnbits#67's per-user
Stripe Connect credentials will plug into; chatelet stores no credentials.

Both rails now go through create_payment_request: Lightning unchanged
(sats, deposit_sat), card charges the same deposit share of the fiat price
in the room's currency with extra.checkout parameterising the hosted
Stripe page — success/cancel return to {frontend}/chatelet/{room}?checkout=…
&booking=<id>, customer_email, line item, metadata. frontend_url is
allow-listed against the instance's trusted origins (ported from events)
and resolved before the hold so a refused rail never leaves a dead hold.
Core settles the Stripe webhook onto the same invoice queue, so
tasks.on_invoice_paid confirms card bookings unchanged.

BookingRequestData gains payment_method / fiat_provider / frontend_url;
BookingQuote gains fiat_payment_request / fiat_provider / is_fiat and a
nullable payment_request. RPC chatelet_booking_request passes the fields
through. min_lnbits_version → 1.4.1 (events' floor for these APIs).

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

views_api.py

@@ -7,7 +7,7 @@ endpoints (room/block CRUD, settings) are HTTP-only and back the admin UI;
 the guest-facing surface (availability, booking) is what also rides the RPC.
 """
 
-from fastapi import APIRouter, Depends, HTTPException, Query
+from fastapi import APIRouter, Depends, HTTPException, Query, Request
 from lnbits.core.models import User, WalletTypeInfo
 from lnbits.decorators import check_user_exists, require_admin_key, require_invoice_key
 
@@ -277,9 +277,13 @@ async def api_check_availability(q: AvailabilityQuery) -> AvailabilityResult:
 
 
 @chatelet_api_router.post("/api/v1/bookings", status_code=201)
-async def api_request_booking(data: BookingRequestData) -> BookingQuote:
+async def api_request_booking(
+    data: BookingRequestData, request: Request
+) -> BookingQuote:
     try:
-        return await services.request_booking(data)
+        return await services.request_booking(
+            data, base_url=str(request.base_url)
+        )
     except services.BookingError as exc:
         raise HTTPException(502, str(exc)) from exc
     except ValueError as exc: