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/resync/route.ts

@@ -2,7 +2,7 @@ import { existsSync } from "node:fs";
 import { asc, inArray, sql } from "drizzle-orm";
 import { apiOk } from "@/lib/api";
 import { withAdmin } from "@/lib/api-handler";
-import { db, ItemsBase } from "@/lib/db";
+import { db, ItemsBase, queryRows } from "@/lib/db";
 import { PERMS } from "@/lib/permissions";
 import {
 	appendFurniEntriesBatch,
@@ -221,7 +221,7 @@ async function resolveTargetIds(
 		Date.now() - days * 24 * 60 * 60 * 1000,
 	).toISOString();
 	const sinceMysql = sinceIso.slice(0, 19).replace("T", " ");
-	const [auditRows] = (await db.execute(sql`
+	const auditRows = await queryRows<{ target_id: number }>(sql`
     SELECT DISTINCT target_id
     FROM admin_audit_log
     WHERE action = 'furni_import'
@@ -229,6 +229,6 @@ async function resolveTargetIds(
       AND target_id IS NOT NULL
       AND created_at >= ${sinceMysql}
     ORDER BY target_id ASC
-  `)) as unknown as [Array<{ target_id: number }>, unknown];
+  `);
 	return auditRows.map((r) => r.target_id).filter(Boolean);
 }