feat(workflows): per-quote booking-workflow picker + quote→invoice (no gallery) built-in

A quote can now choose which flow runs on acceptance instead of every enabled
quote.accepted flow firing. Migration 147 adds quotes.booking_workflow_id; the
editor shows a "Booking workflow (on acceptance)" dropdown listing the
quote.accepted flows (workflow-engine flag only); emitQuoteEvent passes it as
the new emitWorkflowEvent targetWorkflowId so ONLY the picked flow runs (still
gated on enabled + trigger match → a disabled/None selection runs nothing).

Adds the booking_invoice_only built-in (quote.accepted → prepare invoice →
review gate → send; no event/gallery, no wait), the variant requested for
shoots billed without an online gallery. Disabled stub like the other booking
flows until the prepare_*/send_document cutover.

Tests: targetWorkflowId runs only the selected flow; invoice-only built-in has
no wait/prepare_event.

backend/src/routes/adminQuotes.js

@@ -87,6 +87,7 @@ function transformQuote(q) {
     eventName: q.event_name,
     eventDate: q.event_date,
     eventType: q.event_type ?? null,
+    bookingWorkflowId: q.booking_workflow_id ?? null,
     eventTimeStart: q.event_time_start,
     eventTimeEnd: q.event_time_end,
     expectedDurationHours: q.expected_duration_hours == null ? null : Number(q.expected_duration_hours),
@@ -214,6 +215,7 @@ function mapPayloadToService(body) {
     language: 'language', currency: 'currency',
     issueDate: 'issueDate', validUntil: 'validUntil',
     eventName: 'eventName', eventDate: 'eventDate', eventType: 'eventType',
+    bookingWorkflowId: 'bookingWorkflowId',
     eventTimeStart: 'eventTimeStart', eventTimeEnd: 'eventTimeEnd',
     expectedDurationHours: 'expectedDurationHours',
     paymentTermTemplateId: 'paymentTermTemplateId',