DRY pass #3: the web asks one question about a password's length (#5373)

RegisterView and ResetPasswordView each wrote the min-length check and its
message; config.passwordRefusal(password) is that check, the web's side of
auth._password_refusal.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/stores/config.ts

@@ -73,6 +73,14 @@ export const useConfigStore = defineStore("config", () => {
   const minPasswordLength = ref(8);
   const loaded = ref(false);
 
+  // Why the server would refuse this password, said before asking it; null when it
+  // would take it. The server checks again (auth._password_refusal).
+  function passwordRefusal(password: string): string | null {
+    return password.length < minPasswordLength.value
+      ? `Password must be at least ${minPasswordLength.value} characters.`
+      : null;
+  }
+
   async function load(): Promise<void> {
     if (loaded.value) return;
     try {
@@ -106,6 +114,7 @@ export const useConfigStore = defineStore("config", () => {
     clients,
     passwordResetByEmail,
     minPasswordLength,
+    passwordRefusal,
     loaded,
     load,
     reload,

frontend/src/views/RegisterView.vue

@@ -24,11 +24,8 @@ const error = ref("");
 const loading = ref(false);
 
 async function submit() {
-  error.value = "";
-  if (password.value.length < config.minPasswordLength) {
-    error.value = `Password must be at least ${config.minPasswordLength} characters.`;
-    return;
-  }
+  error.value = config.passwordRefusal(password.value) ?? "";
+  if (error.value) return;
   loading.value = true;
   try {
     await session.register(email.value, password.value, displayName.value, invite.value || undefined);

frontend/src/views/ResetPasswordView.vue

@@ -25,11 +25,8 @@ const error = ref("");
 const loading = ref(false);
 
 async function submit() {
-  error.value = "";
-  if (password.value.length < config.minPasswordLength) {
-    error.value = `Password must be at least ${config.minPasswordLength} characters.`;
-    return;
-  }
+  error.value = config.passwordRefusal(password.value) ?? "";
+  if (error.value) return;
   if (password.value !== confirm.value) {
     error.value = "The two passwords don't match.";
     return;