Add AssetItemStatus.lost, category filter on /assets page

lost added via ALTER TYPE ... ADD VALUE (hand-written migration, stays an
enum -- see the schema.prisma comment on why: status values are read
directly by business logic like createAssignment()s in_stock gate, a
lookup table would not actually decouple that). IMPORT_STATUS_MAP gains
lost/missing -> lost mappings for CSV import/re-sync.

/assets page gets a Category filter dropdown (alongside the existing
Status/Model/search filters) that also narrows the Model dropdown to that
category -- with 135 models after the 2026-08-24 real-data import, an
unfiltered Model list is unwieldy. Picking a Category resets the Model
filter if the currently-selected model does not belong to it.

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

src/lib/assets.ts

@@ -3,7 +3,7 @@ import { Prisma } from "@prisma/client";
 import { prisma } from "./prisma";
 import { splitCsvLine, splitCsvLines, normalizeHeader, csvField } from "./csv";
 
-export type AssetItemStatus = "in_stock" | "assigned" | "repair" | "retired";
+export type AssetItemStatus = "in_stock" | "assigned" | "repair" | "retired" | "lost";
 
 export interface AssetItemRecord {
   id: string;
@@ -455,6 +455,8 @@ const IMPORT_STATUS_MAP: Record<string, AssetItemStatus> = {
   "in repair": "repair",
   retired: "retired",
   disposed: "retired",
+  lost: "lost",
+  missing: "lost",
 };
 
 function statusFromImportText(text: string): AssetItemStatus | null {