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.

frontend/src/services/quotes.service.ts

@@ -64,6 +64,7 @@ export interface QuoteSummary {
   eventName: string | null;
   eventDate: string | null;
   eventType: string | null;
+  bookingWorkflowId: number | null;
   totalAmountMinor: number;
   sentAt: string | null;
   acceptedAt: string | null;
@@ -180,6 +181,7 @@ export interface QuoteCreatePayload {
   eventName?: string;
   eventDate?: string;
   eventType?: string | null;
+  bookingWorkflowId?: number | null;
   eventTimeStart?: string;
   eventTimeEnd?: string;
   expectedDurationHours?: number;