feat(brand): swap recipient-facing pictureFrame strings to WeVisto

Updated: SPA <title>, PWA manifest name/short_name, iOS web-app title,
"Install"/"Pin to home screen" copy, HomeView empty state, all Twig page
titles (login/register/setup/token/help), and the share-notification
email header. Left alone: the firmware-broadcast SSID PictureFrame-XXXX
(coordinated firmware change needed) and internal code/comment refs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/views/HomeView.vue

@@ -17,7 +17,7 @@
           </svg>
           <p class="home-view__empty-title">Set up your first frame</p>
           <p class="home-view__empty-sub">
-            Power on your pictureFrame device and scan the QR code it displays to get started.
+            Power on your WeVisto frame and scan the QR code it displays to get started.
           </p>
         </div>
       </div>

frontend/src/views/SettingsView.vue

@@ -5,7 +5,7 @@
     <section v-if="!isStandalone" class="settings__section">
       <h2 class="settings__section-title">Install app</h2>
       <p class="settings__hint">
-        Pin pictureFrame to your home screen so it opens like a native app.
+        Pin WeVisto to your home screen so it opens like a native app.
       </p>
       <button
         v-if="canPromptInstall"
@@ -13,7 +13,7 @@
         class="settings__install"
         @click="onNativeInstall"
       >
-        Install pictureFrame
+        Install WeVisto
       </button>
       <button
         v-else