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/pages/PartDetail.tsx

@@ -89,7 +89,7 @@ export default function PartDetail() {
     );
   }
 
-  const eolDate = part.manufacturer.eolDate ? new Date(part.manufacturer.eolDate) : null;
+  const eolDate = part.partModel.eolDate ? new Date(part.partModel.eolDate) : null;
   const pastEol = eolDate ? eolDate.getTime() < Date.now() : false;
 
   return (
@@ -102,7 +102,7 @@ export default function PartDetail() {
           <div>
             <h1 className="font-mono text-lg font-semibold tracking-tight">{part.serialNumber}</h1>
             <p className="text-xs text-muted-foreground">
-              {part.manufacturer.name} · {part.mpn}
+              {part.manufacturer.name} · {part.partModel.mpn}
             </p>
           </div>
         </div>
@@ -132,7 +132,7 @@ export default function PartDetail() {
             <AlertTriangle className="mt-0.5 h-4 w-4 text-warning" />
             <div className="text-sm">
               <span className="font-medium text-foreground">
-                {part.manufacturer.name} reached EOL {eolDate.toLocaleDateString()}.
+                {part.partModel.mpn} reached EOL {eolDate.toLocaleDateString()}.
               </span>{' '}
               <span className="text-muted-foreground">
                 Plan a replacement for this part.
@@ -150,7 +150,7 @@ export default function PartDetail() {
           <CardContent>
             <dl className="space-y-2">
               <DetailRow label="Serial" value={<span className="font-mono text-xs">{part.serialNumber}</span>} />
-              <DetailRow label="MPN" value={part.mpn} />
+              <DetailRow label="MPN" value={part.partModel.mpn} />
               <DetailRow
                 label="Manufacturer"
                 value={