Accumulate lifecycle total loss across events

[trietmnj]

• Problem: computeConsequencesMultiHazard assigns StructureTotalLoss and ContentsTotalLoss on every event instead of adding to them, so the lifecycle summary reports only the last event's damage (a DE001 run showed $16.9M against $944.4M summed over its event rows).
• Fix: accumulate with +=. TestComputeConsequencesMultiHazard now asserts both totals equal the sum of its five events' damage (67.5; it was 18.0).

structure 365314, DE001 lifecycle 1 (19 events)

event    damage      before: total = damage    after: total += damage
───────  ──────────  ────────────────────────  ──────────────────────
22       $54,235     $54,235                   $54,235
23–31    $0          $0   ◄ reset each event   $54,235
32       $121,427    $121,427                  $175,662
33–36    $0          $0                        $175,662
37       $1,685      $1,685                    $177,348
                     ────────────────────────  ──────────────────────
summary              $1,685   ✗                $177,348   ✓

[HenryGeorgist]

good catch