feat(07.3-03): frontend remember_me — checkbox + ref threading + store pass-through

- LoginView.vue: add rememberMe ref(false) + "Stay signed in for 30 days" checkbox in password step; thread rememberMe.value through all 3 submit handlers (submitPassword, submitTotp, submitBackupCode) (D-12)
- stores/auth.js: login() forwards options.rememberMe as remember_me in api.login body (D-12)
- api/client.js: no change needed — already forwards full body verbatim
- Frontend build passes (vite build exits 0)

frontend/src/stores/auth.js

@@ -66,6 +66,7 @@ export const useAuthStore = defineStore('auth', () => {
         password,
         totp_code: options.totpCode ?? null,
         backup_code: options.backupCode ?? null,
+        remember_me: options.rememberMe ?? false,
       })
 
       if (data.requires_totp) {

frontend/src/views/auth/LoginView.vue

@@ -27,6 +27,17 @@
           />
         </div>
 
+        <!-- Stay signed in checkbox (D-12) -->
+        <div class="flex items-center gap-2">
+          <input
+            v-model="rememberMe"
+            id="remember-me"
+            type="checkbox"
+            class="rounded border-gray-300 text-indigo-600 focus:ring-indigo-500"
+          />
+          <label for="remember-me" class="text-sm text-gray-600">Stay signed in for 30 days</label>
+        </div>
+
         <!-- Form-level error -->
         <div
           v-if="error"
@@ -191,6 +202,7 @@ const totpInput = ref('')
 const backupCodeInput = ref('')
 const loading = ref(false)
 const error = ref(null)
+const rememberMe = ref(false)
 
 // Step: 'password' | 'totp' | 'backup'
 const step = ref('password')
@@ -225,7 +237,7 @@ async function submitPassword() {
   loading.value = true
   error.value = null
   try {
-    const result = await authStore.login(email.value, password.value)
+    const result = await authStore.login(email.value, password.value, { rememberMe: rememberMe.value })
     await handleLoginResult(result)
   } catch (e) {
     error.value = e.message
@@ -240,6 +252,7 @@ async function submitTotp() {
   try {
     const result = await authStore.login(email.value, password.value, {
       totpCode: totpInput.value,
+      rememberMe: rememberMe.value,
     })
     await handleLoginResult(result)
   } catch (e) {
@@ -255,6 +268,7 @@ async function submitBackupCode() {
   try {
     const result = await authStore.login(email.value, password.value, {
       backupCode: backupCodeInput.value,
+      rememberMe: rememberMe.value,
     })
     await handleLoginResult(result)
   } catch (e) {