[FIX] stock_landed_cost: allow reversing valuation via negative quantity + safer cancel/unlink

- Support negative costs by creating reverse valuation move,
  and undoing the quant computation.
  This may or may not produce the exact reverse effect on
  the quant, as it depends on the rounding of the unit
  cost, which uses decimal precision 'Account'
- Hide 'compute' button when cost is not draft
- Forbid cancel of posted cost
- Forbid deletion of cost if not draft

0 files changed, 0 insertions, 0 deletions