feat(parts): couple state and location (host vs bin)

DEPLOYED parts live on a host; every other state lives in a bin (or
unassigned). Previously binId and hostId were independent nullable
fields with no validation, so the Edit Part dialog could leave a
DEPLOYED part with only a bin and no host — which silently dropped
it from the repair problem-part picker.

- Service: resolveLocation() helper enforces the invariant on create
  and update. On a state transition, update auto-clears the stale
  relation and emits LOCATION_CHANGED for the cleared side.
- Zod: CreatePartRequest.superRefine rejects mismatched state/location
  up front; UpdatePartRequest rejects both-fields-set.
- Web: PartFormDialog swaps a single Location field between Host
  combobox (DEPLOYED) and Bin combobox (others); switching State
  clears the opposite field. Parts list + detail render host first,
  then bin path, then Unassigned.
- Tests: 9 new cases covering the invariant including the no-op guard
  so an unrelated PATCH on a DEPLOYED part doesn't touch hostId/binId.

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

packages/shared/src/parts.ts

@@ -42,6 +42,30 @@ export const CreatePartRequest = z
         path: ['partModelId'],
       });
     }
+    // State/location coupling: DEPLOYED parts live on a host; every other state lives in a bin.
+    const state = v.state ?? 'SPARE';
+    if (state === 'DEPLOYED') {
+      if (!v.hostId) {
+        ctx.addIssue({
+          code: z.ZodIssueCode.custom,
+          message: 'A deployed part must be assigned to a host',
+          path: ['hostId'],
+        });
+      }
+      if (v.binId) {
+        ctx.addIssue({
+          code: z.ZodIssueCode.custom,
+          message: 'A deployed part cannot also be in a storage bin',
+          path: ['binId'],
+        });
+      }
+    } else if (v.hostId) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: 'Only deployed parts can be assigned to a host',
+        path: ['hostId'],
+      });
+    }
   });
 export type CreatePartRequest = z.infer<typeof CreatePartRequest>;
 
@@ -57,7 +81,11 @@ export const UpdatePartRequest = z
     categoryId: z.string().uuid().nullable().optional(),
     tagIds: z.array(z.string().uuid()).max(32).optional(),
   })
-  .refine((v) => Object.keys(v).length > 0, { message: 'At least one field required' });
+  .refine((v) => Object.keys(v).length > 0, { message: 'At least one field required' })
+  .refine((v) => !(v.binId && v.hostId), {
+    message: 'A part cannot be assigned to both a host and a bin',
+    path: ['binId'],
+  });
 export type UpdatePartRequest = z.infer<typeof UpdatePartRequest>;
 
 export const PartListQuery = PaginationQuery.extend({