refactor(db): typed query helpers, shared test FormData helper

Replace raw db.execute tuple casts with queryRows/rowsFrom/execResult/
affectedRows helpers from lib/db, drop redundant mysql2 casts on typed
query builders, and centralize per-test fakeForm into test/fake-form.
Update db mocks in tests so helpers resolve against mocked execute.

src/app/api/admin/import/furni/route.ts

@@ -3,7 +3,7 @@ import path from "node:path";
 import { eq, sql } from "drizzle-orm";
 import { apiError, apiOk } from "@/lib/api";
 import { withAdmin } from "@/lib/api-handler";
-import { db, ItemsBase } from "@/lib/db";
+import { db, ItemsBase, queryRows } from "@/lib/db";
 import { normalizeClassname } from "@/lib/furni/classname";
 import { localFurnitureStatus } from "@/lib/furni/local-presence";
 import { PERMS } from "@/lib/permissions";
@@ -184,21 +184,18 @@ export const GET = withAdmin(
 			);
 			const perPage = 500;
 
-			const [importedItems] = (await db.execute(sql`
+			const importedItems = await queryRows<{
+				item_name: string;
+				public_name: string;
+				sprite_id: number;
+				type: string;
+			}>(sql`
         SELECT ib.item_name, ib.public_name, ib.sprite_id, ib.type FROM items_base ib
         WHERE EXISTS (
           SELECT 1 FROM catalog_items ci
           WHERE FIND_IN_SET(ib.id, REPLACE(ci.item_ids, ';', ',')) > 0
         )
-      `)) as unknown as [
-				Array<{
-					item_name: string;
-					public_name: string;
-					sprite_id: number;
-					type: string;
-				}>,
-				unknown,
-			];
+      `);
 
 			// Filter to only those missing .nitro on filesystem (memoized — fast)
 			const missing = importedItems.filter((item) => {