refactor: extract shared login credential verification into auth/login-core

The username normalization, dummy-hash constant, password check and
email-verification gate were duplicated between precheckLogin and the
NextAuth credentials authorize handler. Move them into a single
login-core module so both paths share one source of truth and stay
consistent.

src/actions/auth-precheck.test.ts

@@ -1,19 +1,25 @@
 // @ts-nocheck
 import { beforeEach, describe, expect, it, vi } from "vitest";
-import { checkLogin } from "@/lib/auth/password";
 import { clientIp, rateLimit } from "@/lib/rate-limit";
 import { captchaConfig, verifyCaptcha } from "@/lib/services/captcha";
 import { siteSettings } from "@/lib/services/site-settings";
 import { precheckLogin } from "./auth-precheck";
 
-const { queryPreparedOne } = vi.hoisted(() => {
-	const queryPreparedOne = vi.fn().mockResolvedValue(null);
-	return { queryPreparedOne };
-});
+const core = vi.hoisted(() => ({
+	getLoginUser: vi.fn(),
+	verifyLoginPassword: vi.fn(),
+	isEmailUnverified: vi.fn(),
+	runDummyHashCheck: vi.fn(),
+	normalizeLoginInput: (username: unknown, password: unknown) => ({
+		username: String(username ?? "")
+			.normalize("NFC")
+			.trim(),
+		password: String(password ?? "").normalize("NFC"),
+	}),
+}));
 
 vi.mock("@/env", () => ({ env: { CONVERT_PASSWORDS: false } }));
-vi.mock("@/lib/auth/password", () => ({ checkLogin: vi.fn() }));
-vi.mock("@/lib/db", () => ({ queryPreparedOne }));
+vi.mock("@/lib/auth/login-core", () => core);
 vi.mock("@/lib/rate-limit", () => ({ clientIp: vi.fn(), rateLimit: vi.fn() }));
 vi.mock("@/lib/services/captcha", () => ({
 	captchaConfig: vi.fn(),
@@ -23,33 +29,35 @@ vi.mock("@/lib/services/site-settings", () => ({
 	siteSettings: { getBool: vi.fn() },
 }));
 
+const user = (overrides = {}) => ({
+	password: "hash",
+	twoFactorConfirmedAt: null,
+	mail: null,
+	mailVerified: "0",
+	...overrides,
+});
+
 beforeEach(() => {
 	vi.clearAllMocks();
 	vi.mocked(clientIp).mockResolvedValue("1.2.3.4");
 	vi.mocked(rateLimit).mockResolvedValue({ ok: true });
-	vi.mocked(checkLogin).mockResolvedValue({ valid: true } as never);
 	vi.mocked(captchaConfig).mockResolvedValue({ provider: "none" } as never);
-	queryPreparedOne.mockResolvedValue(null);
+	core.getLoginUser.mockResolvedValue(null);
+	core.verifyLoginPassword.mockResolvedValue({ valid: true });
+	core.isEmailUnverified.mockResolvedValue(false);
+	core.runDummyHashCheck.mockResolvedValue(undefined);
 });
 
 describe("precheckLogin", () => {
 	it("returns ok for valid login without 2FA", async () => {
-		queryPreparedOne.mockResolvedValue({
-			password: "hash",
-			twoFactorConfirmedAt: null,
-			mail: null,
-			mailVerified: "0",
-		});
+		core.getLoginUser.mockResolvedValue(user());
 		expect(await precheckLogin("user", "pass")).toBe("ok");
 	});
 
 	it("returns twofactor when 2FA is set up", async () => {
-		queryPreparedOne.mockResolvedValue({
-			password: "hash",
-			twoFactorConfirmedAt: new Date(),
-			mail: null,
-			mailVerified: "0",
-		});
+		core.getLoginUser.mockResolvedValue(
+			user({ twoFactorConfirmedAt: new Date() }),
+		);
 		expect(await precheckLogin("user", "pass")).toBe("twofactor");
 	});
 
@@ -62,30 +70,20 @@ describe("precheckLogin", () => {
 			provider: "hcaptcha",
 		} as never);
 		vi.mocked(verifyCaptcha).mockResolvedValue(false);
-		queryPreparedOne.mockResolvedValue({
-			password: "hash",
-			twoFactorConfirmedAt: null,
-			mail: null,
-			mailVerified: "0",
-		});
+		core.getLoginUser.mockResolvedValue(user());
 		expect(await precheckLogin("user", "pass", "bad-token")).toBe("captcha");
 	});
 
 	it("returns invalid when user not found (dummy hash check)", async () => {
-		queryPreparedOne.mockResolvedValue(null);
+		core.getLoginUser.mockResolvedValue(null);
 		const result = await precheckLogin("nonexistent", "pass");
 		expect(result).toBe("invalid");
-		expect(checkLogin).toHaveBeenCalled();
+		expect(core.runDummyHashCheck).toHaveBeenCalled();
 	});
 
 	it("returns unverified when email verification required", async () => {
-		queryPreparedOne.mockResolvedValue({
-			password: "hash",
-			twoFactorConfirmedAt: null,
-			mail: "[email protected]",
-			mailVerified: "0",
-		});
-		vi.mocked(siteSettings.getBool).mockResolvedValue(true);
+		core.getLoginUser.mockResolvedValue(user({ mail: "[email protected]" }));
+		core.isEmailUnverified.mockResolvedValue(true);
 		expect(await precheckLogin("user", "pass")).toBe("unverified");
 	});
 });