Confirms an existing shipment using its order number (PRO number).
Moves the shipment from INITIALIZED to CONFIRMED state.

Prerequisites:

• The order must be in INITIALIZED state
• The order must have an associated quote

Validation Requirements:

The following fields are validated during confirmation. If any are missing or invalid,
the shipment will remain in INITIALIZED state.

Address Fields (required on BOTH pickup and delivery addresses):

• name - Location/company name
• address1 - Street address
• zipCode - ZIP code
• contactPerson - Contact name
• phoneNumber - Contact phone (E.164 format, e.g., "+15551234567")
• openTime - Opening time in HH:mm format (defaults to "10:00")
• closeTime - Closing time in HH:mm format (defaults to "16:00")

Order Fields:

• description - Must not be empty
• totalPalletCount - At least 1, up to the current per-order maximum
• totalPoundsWeight - At least 1, within the current per-pallet weight cap

Order Component Fields (per component):

• palletCount - Must be at least 1
• poundsWeight - At least 1, within the current per-pallet weight cap
• palletDimensions - Length, width and height in inches, each at least 1 and
  within the current maximums. These limits are configurable and change over
  time, so they are not restated here: a pallet that exceeds them is rejected
  with a 422 whose violation message states the maximum that applied. A pallet
  larger than the standard footprint is still accepted and priced as oversized,
  and a stop that requires a liftgate applies a tighter maximum.

Component Totals:

• Sum of component palletCount must equal order totalPalletCount
• Sum of component poundsWeight must equal order totalPoundsWeight