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-help.test.ts

@@ -1,6 +1,7 @@
 import { redirect } from "next/navigation";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import { requirePermission } from "@/lib/admin/guard";
+import { fakeForm } from "@/test/fake-form";
 import {
 	createHelpQuestion,
 	deleteHelpQuestion,
@@ -29,10 +30,6 @@ 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 | null>) => ({
-	get: (key: string) => (key in data ? data[key] : null),
-});
-
 beforeEach(() => {
 	vi.clearAllMocks();
 	vi.mocked(requirePermission).mockResolvedValue(staff as never);
@@ -47,7 +44,7 @@ describe("createHelpQuestion", () => {
 			fakeForm({
 				name: "FAQ",
 				content: "<p>Answer</p>",
-			}) as unknown as FormData,
+			}) as FormData,
 		);
 		expect(insertValues).toHaveBeenCalled();
 		expect(redirect).toHaveBeenCalledWith("/admin/help-questions");
@@ -61,7 +58,7 @@ describe("updateHelpQuestion", () => {
 				id: "42",
 				name: "Updated",
 				content: "New",
-			}) as unknown as FormData,
+			}) as FormData,
 		);
 		expect(updateWhere).toHaveBeenCalled();
 		expect(redirect).toHaveBeenCalledWith("/admin/help-questions");
@@ -70,7 +67,7 @@ describe("updateHelpQuestion", () => {
 
 describe("deleteHelpQuestion", () => {
 	it("deletes and redirects", async () => {
-		await deleteHelpQuestion(fakeForm({ id: "42" }) as unknown as FormData);
+		await deleteHelpQuestion(fakeForm({ id: "42" }) as FormData);
 		expect(deleteWhere).toHaveBeenCalled();
 		expect(redirect).toHaveBeenCalledWith("/admin/help-questions");
 	});