## Description of the issue

Stock valuation is recorded per move: the value stored on an outgoing move is
`quantity * standard price` at **validation** time. When moves are validated
out of chronological order (backdated receipts) or deliveries are returned,
those recorded values diverge from the weighted average that results from
walking the moves in date order, which is how the inventory valuation at date
(`_run_average_batch(at_date)`) computes the stock value.

The PLE 13.1 report (Registro de Inventario Permanente Valorizado, SUNAT)
summed the recorded values, so its balances did not match the Inventory at
Date report nor the stock closing entries, and an auditor recomputing the
weighted average in date order could not reproduce the outgoing costs line by
line.

## Steps to reproduce

1. PE company, AVCO product.
2. Receive 10 units at 100. Deliver 5 units (valued 5 x 100 = 500).
3. Receive 10 units at 200, then set the move date **before** the delivery.
4. Generate PLE 13.1 for the period and compare with the Inventory at Date
   report at the period end.

Current behavior: the delivery line shows 500 and the ending balance 2,500,
while the Inventory at Date report shows 2,250.

Expected behavior: the delivery is valued at the date-ordered average
(5 x 150 = 750) and the ending balance (2,250) matches the valuation at date.

## Solution

Value outgoing lines of average costed products with the running average
maintained in date order, seed it from the recomputed opening balance
(reusing `product.product._run_average_batch()`), and reset it from the
receipt unit cost when the previous quantity is not positive, replicating the
valuation-at-date walk. Opening and historic balance lines use the same
recomputed value.

Products with standard or FIFO cost methods keep the recorded values. Manual
standard price revaluations dated inside the reported period are not replayed
by the period walk.

task-100934