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/lib/services/furni-data.ts

@@ -1,7 +1,7 @@
 import { existsSync, promises as fs } from "node:fs";
 import path from "node:path";
 import { eq, sql } from "drizzle-orm";
-import { db, ItemsBase } from "@/lib/db";
+import { db, execResult, ItemsBase, queryRows } from "@/lib/db";
 import {
 	getGamedataRoot,
 	getNitroFilesRoot,
@@ -698,14 +698,14 @@ export interface CatalogOfferRebuildResult {
  */
 export async function rebuildCatalogOfferIds(): Promise<CatalogOfferRebuildResult> {
 	return withFurniDataLock(async () => {
-		const [countRows] = (await db.execute(
+		const countRows = await queryRows<{ total: number }>(
 			sql`SELECT COUNT(*) AS total FROM catalog_items`,
-		)) as unknown as [Array<{ total: number }>, unknown];
+		);
 		const checked = Number(countRows?.[0]?.total ?? 0);
 
-		const [result] = (await db.execute(sql`
+		const result = await execResult(sql`
       UPDATE catalog_items SET offer_id = id WHERE offer_id <> id
-    `)) as unknown as [Record<string, unknown>, unknown];
+    `);
 
 		return { checked, fixed: Number(result.affectedRows ?? 0) };
 	});