Owner calendar view + manual booking + owner cancel/reschedule (#20)

Adds an owner-authenticated weekly agenda (grouped by day, today highlighted)
with manual walk-in/phone booking creation, cancel, and reschedule -- all
routed through booking_api.py's create/cancel/reschedule logic (refactored
into shared helpers) so the EXCLUDE overlap constraint and confirmation
email stay on the single existing code path. Manual creation can skip the
opening-hours/min-notice/max-advance/buffer checks via an explicit override,
but never the overlap constraint itself.

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

backoffice/app/app.py

@@ -25,12 +25,14 @@ from booking_api import bp as booking_bp
 from public_booking import bp as public_booking_bp
 from manage_booking import bp as manage_booking_bp
 from owner_auth import bp as owner_auth_bp
+from owner_booking import bp as owner_booking_bp
 
 app = Flask(__name__, static_folder="static", static_url_path="")
 app.register_blueprint(booking_bp)
 app.register_blueprint(public_booking_bp)
 app.register_blueprint(manage_booking_bp)
 app.register_blueprint(owner_auth_bp)
+app.register_blueprint(owner_booking_bp)
 
 # Dedicated secret for the owner-login session cookie -- deliberately not
 # shared with CRM_API_TOKEN or BOOKING_TOKEN_SECRET (#19), same reasoning as