feat(parts): make MPN and manufacturer cells clickable

MPN links to /part-models/:id and manufacturer links to
/manufacturers/:id, matching the cross-navigation pattern used on
other detail and table views.

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

apps/web/src/pages/Parts.tsx

@@ -116,14 +116,24 @@ export default function Parts() {
         id: 'mpn',
         header: 'MPN',
         cell: ({ row }) => (
-          <span className="text-sm font-mono">{row.original.partModel.mpn}</span>
+          <Link
+            to={`/part-models/${row.original.partModelId}`}
+            className="text-sm font-mono hover:underline"
+          >
+            {row.original.partModel.mpn}
+          </Link>
         ),
       },
       {
         id: 'manufacturer',
         header: 'Manufacturer',
         cell: ({ row }) => (
-          <span className="text-sm text-muted-foreground">{row.original.manufacturer.name}</span>
+          <Link
+            to={`/manufacturers/${row.original.manufacturerId}`}
+            className="text-sm text-muted-foreground hover:underline"
+          >
+            {row.original.manufacturer.name}
+          </Link>
         ),
       },
       {