Add AssetItem.areaId, show assigned-to + area on /assets, mm/dd/yyyy dates

AssetItem.areaId reuses the existing Area entity (built for InventoryScan/
the office-move feature) rather than a free-text location string -- same
share-the-lookup-entity precedent floated for Department. Real-world
coverage from the ITAM export is thin: Physical location was the literal
string DAN for all 613 rows (useless), only Stockroom carried signal, and
only for the ~71 in_stock items -- an assigned item is with a person, not
in a stockroom bin, so most rows have no area by design, not by gap.

/assets page: the assigned employee (via the active, non-returned
Assignment) was already in the DB from the 2026-08-24 backfill but never
shown -- added an Assigned To column, folded into the free-text search
too. Added an Area column + filter dropdown. Removed the Created At
column (not actionable) and format Purchase Date/Warranty End Date as
mm/dd/yyyy instead of raw ISO strings.

CSV import/export: area column added (resolved/created via
createOrGetArea(), same idempotent-by-name helper the bots Area picker
uses -- not a raw UUID). Re-ran the 613-row import after this: 0 created,
613 updated, 0 errors -- backfilled area onto the 71 rows with a
Stockroom value (46 IT Cabinet, 21 Stockroom, 4 For allocation), verified
against the source file.

Hand-written migration, no Vitest coverage -- same deviation as the rest
of this branch, see CLAUDE.md. tsc/lint clean.

src/lib/assets.ts

@@ -2,6 +2,7 @@ import { z } from "zod";
 import { Prisma } from "@prisma/client";
 import { prisma } from "./prisma";
 import { splitCsvLine, splitCsvLines, normalizeHeader, csvField } from "./csv";
+import { createOrGetArea } from "./areas";
 
 export type AssetItemStatus = "in_stock" | "assigned" | "repair" | "retired" | "lost";
 
@@ -15,6 +16,7 @@ export interface AssetItemRecord {
   status: AssetItemStatus;
   cost: number | null;
   cost_currency: string | null;
+  area_id: string | null;
   purchase_order_id: string | null;
   // Free-text PO number from an external system -- NOT purchase_order_id
   // above (a real FK). See schema.prisma's AssetItem.externalPoNumber
@@ -37,6 +39,7 @@ export interface CreateAssetItemInput {
   warrantyEndDate?: Date;
   cost?: number | null;
   costCurrency?: string | null;
+  areaId?: string | null;
   purchaseOrderId?: string | null;
   externalPoNumber?: string | null;
   // Only set by importAssetItems() (bulk-loading already-deployed
@@ -112,6 +115,11 @@ const createAssetItemSchema = z.object({
     .string({ invalid_type_error: "externalPoNumber must be a string" })
     .optional()
     .nullable(),
+  areaId: z
+    .string({ invalid_type_error: "areaId must be a valid UUID string" })
+    .uuid("areaId must be a valid UUID string")
+    .optional()
+    .nullable(),
 });
 
 /**
@@ -139,6 +147,7 @@ export function validateCreateAssetItemInput(input: {
   cost?: unknown;
   costCurrency?: unknown;
   externalPoNumber?: unknown;
+  areaId?: unknown;
 }): ValidationResult {
   const result = createAssetItemSchema.safeParse(input);
   if (!result.success) {
@@ -158,6 +167,7 @@ function toRecord(row: {
   status: AssetItemStatus;
   cost: Prisma.Decimal | null;
   costCurrency: string | null;
+  areaId: string | null;
   purchaseOrderId: string | null;
   externalPoNumber: string | null;
   createdAt: Date;
@@ -172,6 +182,7 @@ function toRecord(row: {
     status: row.status,
     cost: row.cost ? row.cost.toNumber() : null,
     cost_currency: row.costCurrency,
+    area_id: row.areaId,
     purchase_order_id: row.purchaseOrderId,
     external_po_number: row.externalPoNumber,
     created_at: row.createdAt.toISOString(),
@@ -247,6 +258,7 @@ export async function createAssetItem(
         warrantyEndDate,
         cost: input.cost ?? null,
         costCurrency: input.costCurrency ?? null,
+        areaId: input.areaId ?? null,
         purchaseOrderId: input.purchaseOrderId ?? null,
         externalPoNumber: input.externalPoNumber ?? null,
         ...(input.status ? { status: input.status } : {}),
@@ -264,10 +276,15 @@ export async function createAssetItem(
       return { ok: false, error: "serialNumber already exists" };
     }
     if (error instanceof Prisma.PrismaClientKnownRequestError && error.code === "P2003") {
+      // Three FKs can fail here now (modelId, purchaseOrderId, areaId) --
+      // field_name says which constraint actually fired.
       const fieldName = typeof error.meta?.field_name === "string" ? error.meta.field_name : "";
       if (fieldName.includes("purchase_order")) {
         return { ok: false, error: "purchaseOrderId does not reference an existing purchase order" };
       }
+      if (fieldName.includes("area")) {
+        return { ok: false, error: "areaId does not reference an existing area" };
+      }
       return { ok: false, error: "modelId does not reference an existing asset model" };
     }
     throw error;
@@ -314,6 +331,11 @@ export interface ImportAssetItemRow {
   // NOT the same as purchaseOrderId above -- see schema.prisma's
   // AssetItem.externalPoNumber comment.
   externalPoNumber: string | null;
+  // Area name, resolved/created via src/lib/areas.ts's createOrGetArea()
+  // (idempotent by name, same as the bot's Area picker) -- not a raw UUID
+  // column like the other FK-ish fields here, since a hand-edited
+  // spreadsheet realistically has area names, not this app's internal ids.
+  areaName: string | null;
 }
 
 const ASSET_ITEM_HEADER_ALIASES: Record<keyof ImportAssetItemRow, string[]> = {
@@ -350,6 +372,7 @@ const ASSET_ITEM_HEADER_ALIASES: Record<keyof ImportAssetItemRow, string[]> = {
   // actual "PO number" column name 1:1, and keeps the two fields
   // unambiguous from each other by header name alone.
   externalPoNumber: ["ponumber", "po number", "external po number", "so po"],
+  areaName: ["area", "khu vuc", "location", "stockroom", "vi tri"],
 };
 
 export type ParseAssetItemsCsvResult =
@@ -422,6 +445,7 @@ export function parseAssetItemsCsv(text: string): ParseAssetItemsCsvResult {
       cost: get("cost") || null,
       costCurrency: get("costCurrency") || null,
       externalPoNumber: get("externalPoNumber") || null,
+      areaName: get("areaName") || null,
     };
     if (!row.serialNumber && !row.manufacturer && !row.modelName && !row.purchaseDate) {
       continue; // fully blank row
@@ -566,6 +590,22 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
     const costCurrency = cleanImportText(row.costCurrency);
     const externalPoNumber = cleanImportText(row.externalPoNumber);
 
+    // Resolved via createOrGetArea() (idempotent by name -- same helper
+    // the bot's Area picker uses), not a raw areaId column: a hand-edited
+    // spreadsheet realistically has area *names*, and this also means a
+    // never-before-seen area name just gets created rather than rejecting
+    // the row.
+    let areaId: string | undefined;
+    const areaName = cleanImportText(row.areaName);
+    if (areaName) {
+      const areaResult = await createOrGetArea({ name: areaName });
+      if (!areaResult.ok) {
+        errors.push({ row: rowNumber, serialNumber: row.serialNumber, error: `Area error: ${areaResult.error}` });
+        continue;
+      }
+      areaId = areaResult.value.id;
+    }
+
     const model = await prisma.assetModel.findFirst({
       where: {
         manufacturer: { equals: row.manufacturer, mode: "insensitive" },
@@ -606,6 +646,7 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
           ...(costCurrency ? { costCurrency } : {}),
           ...(row.purchaseOrderId ? { purchaseOrderId: row.purchaseOrderId } : {}),
           ...(externalPoNumber ? { externalPoNumber } : {}),
+          ...(areaId ? { areaId } : {}),
         },
       });
       updated++;
@@ -623,6 +664,7 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
       costCurrency,
       purchaseOrderId: row.purchaseOrderId ?? undefined,
       externalPoNumber,
+      areaId,
     });
     if (!result.ok) {
       errors.push({ row: rowNumber, serialNumber: row.serialNumber, error: result.error });
@@ -644,7 +686,7 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
  */
 export async function exportAssetItemsCsv(): Promise<string> {
   const rows = await prisma.assetItem.findMany({
-    include: { model: true },
+    include: { model: true, area: true },
     orderBy: [{ createdAt: "desc" }, { id: "desc" }],
   });
 
@@ -658,6 +700,7 @@ export async function exportAssetItemsCsv(): Promise<string> {
     "status",
     "cost",
     "cost_currency",
+    "area",
     "purchase_order_id",
     "external_po_number",
   ];
@@ -673,6 +716,7 @@ export async function exportAssetItemsCsv(): Promise<string> {
       row.status,
       row.cost ? row.cost.toString() : "",
       row.costCurrency ?? "",
+      row.area?.name ?? "",
       row.purchaseOrderId ?? "",
       row.externalPoNumber ?? "",
     ];