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/actions/admin-ads.test.ts

@@ -6,6 +6,7 @@ import { requirePermission } from "@/lib/admin/guard";
 import { logger } from "@/lib/logger";
 import { ActionError } from "@/lib/safe-action-shared";
 import { logStaffActivity } from "@/lib/services/staff-activity";
+import { fakeForm } from "@/test/fake-form";
 import { createAd, deleteAd } from "./admin-ads";
 
 const { insertValues, deleteWhere } = vi.hoisted(() => {
@@ -41,10 +42,6 @@ vi.mock("next/cache", () => ({ revalidatePath: vi.fn() }));
 vi.mock("next/navigation", () => ({ redirect: vi.fn() }));
 
 const staff = { id: 1, rank: 7, username: "admin" };
-const fakeForm = (data: Record<string, string>) => ({
-	get: (k: string) => data[k] ?? null,
-});
-
 beforeEach(() => {
 	vi.clearAllMocks();
 	vi.mocked(requirePermission).mockResolvedValue(staff as never);
@@ -55,7 +52,7 @@ beforeEach(() => {
 describe("createAd", () => {
 	it("creates ad and redirects", async () => {
 		await createAd(
-			fakeForm({ image: "https://example.com/ad.png" }) as unknown as FormData,
+			fakeForm({ image: "https://example.com/ad.png" }) as FormData,
 		);
 		expect(insertValues).toHaveBeenCalled();
 		expect(logStaffActivity).toHaveBeenCalled();
@@ -63,13 +60,13 @@ describe("createAd", () => {
 	});
 
 	it("returns early when image empty", async () => {
-		await createAd(fakeForm({ image: "" }) as unknown as FormData);
+		await createAd(fakeForm({ image: "" }) as FormData);
 		expect(insertValues).not.toHaveBeenCalled();
 	});
 
 	it("logs error on db failure", async () => {
 		insertValues.mockRejectedValue(new Error("db"));
-		await createAd(fakeForm({ image: "x" }) as unknown as FormData);
+		await createAd(fakeForm({ image: "x" }) as FormData);
 		expect(logger.error).toHaveBeenCalled();
 	});
 });