Backoffice: new tab on the booking detail page (?tab=additional-charges,
already linked from the row menu) with an Add Charge modal — Save draft or
Send to customer.
Portal: charges panel on the booking detail page, Pay now per charge via
the existing OTP/CBE-bill payment flow.
Also fixes: GET /bookings/:id/additional-charges was returning DRAFT
charges to the customer (hidden client-side only) — now filtered
server-side per caller.