Owner notification webhook: Telegram re-point (#23)

Flask fires a fire-and-forget internal webhook (owner_notify.py, mirroring
mailer.py's background-thread queue) on booking create/cancel/reschedule,
carrying the same {booking, business_name, notify_channel} shape the old
EA-driven "Build booking row" node produced, plus an event field so the
Telegram message can say what actually happened. n8n/booking-sync.json gets
a new webhook + IF node feeding the existing Telegram node directly, so it
no longer needs EA's API to build the notification payload; channel routing
(only telegram sends for now) lives in that IF node.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backoffice/app/booking_api.py

@@ -15,6 +15,7 @@ from flask import Blueprint, jsonify, request
 import availability
 import booking_db as bdb
 import booking_mail
+import owner_notify
 
 bp = Blueprint("booking_api", __name__, url_prefix="/api/booking")
 
@@ -161,6 +162,7 @@ def create_booking_row(client_id, resource_id, service_id, start_time,
     # owner manual-entry (#20) included -- calling bdb.create_booking()
     # directly would bypass it.
     booking_mail.send_booking_confirmation(client, booking, token)
+    owner_notify.notify(client, booking, "created")  # #23
     return booking, token
 
 
@@ -174,7 +176,9 @@ def cancel_booking_row(client_id, booking_id):
         raise NotFound()
     if existing["status"] == "cancelled":
         raise AlreadyCancelled()
-    return bdb.update_booking(client_id, booking_id, status="cancelled")
+    updated = bdb.update_booking(client_id, booking_id, status="cancelled")
+    owner_notify.notify(bdb.get_client(client_id), updated, "cancelled")  # #23
+    return updated
 
 
 def reschedule_booking_row(client_id, booking_id, new_start):
@@ -203,10 +207,12 @@ def reschedule_booking_row(client_id, booking_id, new_start):
         raise SlotUnavailable()
 
     try:
-        return bdb.update_booking(client_id, booking_id, start_time=new_start,
-                                   end_time=new_end)
+        updated = bdb.update_booking(client_id, booking_id, start_time=new_start,
+                                      end_time=new_end)
     except bdb.BookingConflict:
         raise SlotTaken() from None
+    owner_notify.notify(client, updated, "rescheduled")  # #23
+    return updated
 
 
 class _BadDuration(ValueError):