Show lock icon instead of hiding repeat button, tusky-style. Added hint

explaining what's going on. Fixes favorite button jumping left and right
depending on post visibility

src/components/retweet_button/retweet_button.vue

@@ -1,7 +1,12 @@
 <template>
-  <div v-if="loggedIn && visibility !== 'private' && visibility !== 'direct'">
+  <div v-if="loggedIn">
+    <template v-if="visibility !== 'private' && visibility !== 'direct'">
       <i :class='classes' class='icon-retweet rt-active' v-on:click.prevent='retweet()'></i>
       <span v-if='status.repeat_num > 0'>{{status.repeat_num}}</span>
+    </template>
+    <template v-else>
+      <i :class='classes' class='icon-lock' :title="$t('timeline.no_retweet_hint')"></i>
+    </template>
   </div>
   <div v-else-if="!loggedIn">
     <i :class='classes' class='icon-retweet'></i>

src/i18n/messages.js

@@ -273,7 +273,8 @@ const en = {
     load_older: 'Load older statuses',
     conversation: 'Conversation',
     collapse: 'Collapse',
-    repeated: 'repeated'
+    repeated: 'repeated',
+    no_retweet_hint: 'Post is marked as followers-only or direct and cannot be repeated'
   },
   settings: {
     user_settings: 'User Settings',
@@ -1620,7 +1621,8 @@ const ru = {
     load_older: 'Загрузить старые статусы',
     conversation: 'Разговор',
     collapse: 'Свернуть',
-    repeated: 'повторил(а)'
+    repeated: 'повторил(а)',
+    no_retweet_hint: 'Пост помечен как "только для подписчиков" или "личное" и поэтому не может быть повторён'
   },
   settings: {
     user_settings: 'Настройки пользователя',