Rename AssetItemStatus 'assigned' to 'in_use'

'assigned' implied a specific person always holds the item, but
createAssignment() only requires status=in_stock to hand something out --
the status value itself never guaranteed a matching Assignment row exists.
~158 of the 613 real-imported assets carry this status with no Assignment
at all (shared/unowned equipment like meeting-room gear), so "assigned"
was actively misleading for them. 'in_use' doesn't carry that implication.

DB: `ALTER TYPE "AssetItemStatus" RENAME VALUE 'assigned' TO 'in_use'`
(hand-written migration -- runs cleanly, no data migration needed, every
existing row's status just reads under the new name). Renamed across:
schema.prisma enum, src/lib/assets.ts (type union + IMPORT_STATUS_MAP,
which keeps an `assigned` key mapped to `in_use` for backward-compat with
pre-2026-08-25 exports/CSVs), src/lib/assignments.ts (the literal status
value createAssignment() sets), src/app/assets/page.tsx + api/assets/
route.ts (filter dropdown + validStatuses), src/app/maintenance-records/
page.tsx (its own copy of the status list for the "close" targetStatus
picker). maintenance-records.ts itself needed no logic change -- its
closeableTargetStatusValues was already just ["in_stock", "retired"],
"assigned" was never a valid close target, only mentioned in comments
(updated for accuracy).

Also fixes a real regression found while verifying this: tests/
assets.test.ts (a pre-existing, properly-reviewed test file, not written
this session) broke 2 commits ago when GET /api/assets's signature and
response shape changed for pagination -- it still called GET() with no
Request and expected a bare array. tsc didn't catch this until now
because this container has no dev bind mount (Dockerfile is COPY-based,
`docker exec` only reflects the last build) -- see the
ubi-dan-itam-docker-no-bind-mount memory note. Added a getRequest()
helper and updated assertions to the {items, total} shape.

Verified by actually rebuilding and running the full suite fresh (not
just tsc/lint smoke checks): 369/369 tests pass, including
assignments.test.ts and maintenance-records.test.ts, which this rename
touches directly. tsc/lint clean against the rebuilt image. Migration
applied to the real DB, data verified intact (542 in_use + 71 in_stock =
613, matches pre-rename counts exactly).

tests/assets.test.ts

@@ -24,6 +24,13 @@ function postRequest(body: unknown): Request {
   });
 }
 
+// GET /api/assets takes a Request now (2026-08-25, see route.ts) so it can
+// read pagination/filter query params -- query is an optional raw query
+// string (e.g. "status=in_use&page=2"), empty by default.
+function getRequest(query = ""): Request {
+  return new Request(`http://localhost/api/assets${query ? `?${query}` : ""}`);
+}
+
 // AssetItem.purchaseOrderId is a real FK to PurchaseOrder (see
 // schema.prisma / src/lib/assets.ts), and PurchaseOrder.vendorId is a real
 // FK to Vendor — tests that need a valid purchaseOrderId create real rows
@@ -331,23 +338,26 @@ describe("GET /api/assets", () => {
     await new Promise((resolve) => setTimeout(resolve, 5));
     await POST(postRequest({ serialNumber: "SN-011", modelId, purchaseDate: "2026-02-01" }));
 
-    const res = await GET();
+    const res = await GET(getRequest());
     expect(res.status).toBe(200);
 
+    // {items, total} now (2026-08-25, see listAssetItems()'s doc comment
+    // in src/lib/assets.ts) -- was a bare array before pagination.
     const body = await res.json();
-    expect(Array.isArray(body)).toBe(true);
-    expect(body).toHaveLength(2);
+    expect(Array.isArray(body.items)).toBe(true);
+    expect(body.items).toHaveLength(2);
+    expect(body.total).toBe(2);
 
     // newest first
-    expect(body[0]).toMatchObject({ serial_number: "SN-011", model_id: modelId });
-    expect(body[1]).toMatchObject({ serial_number: "SN-010", model_id: modelId });
+    expect(body.items[0]).toMatchObject({ serial_number: "SN-011", model_id: modelId });
+    expect(body.items[1]).toMatchObject({ serial_number: "SN-010", model_id: modelId });
   });
 
   it("returns an empty list when there are no asset items", async () => {
-    const res = await GET();
+    const res = await GET(getRequest());
     expect(res.status).toBe(200);
     const body = await res.json();
-    expect(body).toEqual([]);
+    expect(body).toEqual({ items: [], total: 0 });
   });
 });
 
@@ -375,7 +385,7 @@ describe("auth gating on /api/assets", () => {
   it("GET /api/assets returns 401 without a session", async () => {
     mockedAuth.mockResolvedValue(null);
 
-    const res = await GET();
+    const res = await GET(getRequest());
 
     expect(res.status).toBe(401);
     const body = await res.json();