feat(auth): make password length configurable via env (min 5–30, max 30–128)

Add PASSWORD_MIN_LENGTH / PASSWORD_MAX_LENGTH (validated in src/env.ts) and a
shared passwordPolicy helper. The policy drives the zod schemas in register,
password reset and the admin create-user dialog, plus the live requirement
checks and strength meter in the register form.

Locale messages now interpolate the configured minimum via {min} instead of
hard-coding 12.

src/actions/password-reset.ts

@@ -6,6 +6,7 @@ import { redirect } from "next/navigation";
 import { env } from "@/env";
 import { invalidateLoginCache } from "@/lib/auth/login-core";
 import { hashPassword } from "@/lib/auth/password";
+import { passwordPolicy } from "@/lib/auth/password-policy";
 import { revokeUserCredentials } from "@/lib/auth/session-revocation";
 import { db, PasswordReset, User } from "@/lib/db";
 import { logger } from "@/lib/logger";
@@ -109,7 +110,11 @@ export async function resetPassword(formData: FormData): Promise<void> {
 	}
 
 	let error: "password" | "invalid" | "failed" | null = null;
-	if (password.length < 12) error = "password";
+	if (
+		password.length < passwordPolicy.minLength ||
+		password.length > passwordPolicy.maxLength
+	)
+		error = "password";
 
 	if (!error) {
 		try {

src/actions/register.ts

@@ -5,6 +5,7 @@ import { after } from "next/server";
 import { z } from "zod";
 import { sendVerification } from "@/lib/auth/email-verification";
 import { hashPassword } from "@/lib/auth/password";
+import { passwordPolicy } from "@/lib/auth/password-policy";
 import { DEFAULT_AVATAR_FIGURE } from "@/lib/avatar-figure";
 import { invalidateKey } from "@/lib/cached-db";
 import { db, User } from "@/lib/db";
@@ -83,6 +84,11 @@ function hasDisposableEmailDomain(email: string): boolean {
 	return domain ? DISPOSABLE_EMAIL_DOMAINS.has(domain) : false;
 }
 
+// Rendered into the schema below and mapped back to a locale-independent code
+// via `ZOD_MESSAGE_CODES`, so the length always reflects the configured policy.
+const PASSWORD_MIN_MESSAGE = `Password must be at least ${passwordPolicy.minLength} characters`;
+const PASSWORD_MAX_MESSAGE = "Password is too long";
+
 const registerSchema = z
 	.object({
 		username: z
@@ -105,8 +111,8 @@ const registerSchema = z
 			),
 		password: z
 			.string()
-			.min(12, "Password must be at least 12 characters") // Increased min length
-			.max(128, "Password is too long") // Added max length
+			.min(passwordPolicy.minLength, PASSWORD_MIN_MESSAGE)
+			.max(passwordPolicy.maxLength, PASSWORD_MAX_MESSAGE)
 			.regex(/[A-Z]/, "Password must contain at least one uppercase letter")
 			.regex(/[a-z]/, "Password must contain at least one lowercase letter")
 			.regex(/[0-9]/, "Password must contain at least one digit")
@@ -160,8 +166,8 @@ const ZOD_MESSAGE_CODES: Record<string, RegisterErrorCode> = {
 	"This username is reserved": "usernameReserved",
 	"Enter a valid email address": "emailValid",
 	"Temporary email domains are not allowed": "emailDisposable",
-	"Password must be at least 12 characters": "passwordMinLength",
-	"Password is too long": "passwordMaxLength",
+	[PASSWORD_MIN_MESSAGE]: "passwordMinLength",
+	[PASSWORD_MAX_MESSAGE]: "passwordMaxLength",
 	"Password must contain at least one uppercase letter": "passwordUpper",
 	"Password must contain at least one lowercase letter": "passwordLower",
 	"Password must contain at least one digit": "passwordDigit",