feat: rework EOL, repairs, and hosts for real workflow

Four domain-model changes driven by exercising the deployed 2.0 build:

- EOL moves from manufacturer to MPN via new PartModel catalog table,
  so alerts fire on the thing that actually ages.
- Repairs re-home to Host (required hostId + problem text) with an
  optional RepairJobPart join for affected parts; drop Part.replacementPartId.
- New /repairs/:id detail page with editable problem, part list, and
  a RepairComment thread (REPAIR_COMMENTED events fan out to each
  problem part's timeline).
- Host.assetId (required, unique) surfaces prominently on the repair
  page so techs can confirm they're touching the right box.

Single destructive migration reshapes existing dev data. All 7 packages
typecheck clean; 30 API tests pass (9 new covering host membership,
upsertByMpn idempotency + race, assetId 409, comment userId stamping).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/components/parts/PartFormDialog.tsx

@@ -80,7 +80,7 @@ export function PartFormDialog({ open, onOpenChange, part }: PartFormDialogProps
       part
         ? {
             serialNumber: part.serialNumber,
-            mpn: part.mpn,
+            mpn: part.partModel.mpn,
             manufacturerId: part.manufacturerId,
             state: part.state,
             binId: part.binId ?? '',