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/(site)/settings/sessions/page.tsx

@@ -4,7 +4,7 @@ import { getTranslations } from "next-intl/server";
 import { signOutEverywhere } from "@/actions/sessions";
 import { ContentCard, EmptyState } from "@/components/public/ui";
 import { auth } from "@/lib/auth";
-import { db, WebsiteLoginLogs } from "@/lib/db";
+import { db, queryRows, WebsiteLoginLogs } from "@/lib/db";
 import { formatDate } from "@/lib/format-date";
 
 type SearchParams = Promise<{ signedOutAll?: string }>;
@@ -69,11 +69,10 @@ export default async function SessionsPage({
 	type Failed = { id: number; ip_address: string; attempted_at: Date | string };
 	let failed: Failed[] = [];
 	try {
-		const [rows] = (await db.execute(sql`
+		failed = await queryRows<Failed>(sql`
 			SELECT id, ip_address, attempted_at FROM failed_logins
 			WHERE username = ${session.user.name} ORDER BY id DESC LIMIT 15
-		`)) as unknown as [Failed[], unknown];
-		failed = rows ?? [];
+		`);
 	} catch {
 		failed = [];
 	}