chore(client): translate all user-visible strings to English

Mixed-language UI was confusing — onboarding said "Why DChain / How it
works / Your keys" in English headings but feature descriptions and
CTAs were in Russian; compose's confirm dialog was Russian; feed tabs
were Russian; error messages in humanizeTxError were Russian.
Everything user-facing is now English.

Files touched (only string literals, not comments):
  app/index.tsx              onboarding slides + CTA buttons
  app/(app)/compose.tsx      composer alerts, header button, placeholder,
                             attachment-size hint
  app/(app)/feed/index.tsx   tab labels (Following/For you/Trending),
                             empty-state hints, retry button
  app/(app)/feed/[id].tsx    post detail header + stats rows (Views,
                             Likes, Size, Paid to publish, Hosted on,
                             Hashtags)
  app/(app)/feed/tag/[tag].tsx  empty-state copy
  app/(app)/profile/[address].tsx  Profile header, Follow/Following,
                             Edit, Open chat, Address, Copied, Encryption,
                             Added, Members, unknown-contact hint
  app/(app)/new-contact.tsx  Search title, placeholder, Search button,
                             empty-state hint, E2E-ready indicator,
                             Intro label + placeholder, fee-tier labels
                             (Min / Standard / Priority), Send request,
                             Insufficient-balance alert, Request-sent
                             alert
  app/(app)/requests.tsx     Notifications title, empty-state, Accept /
                             Decline buttons, decline-confirm alert,
                             "wants to add you" line
  components/SearchBar.tsx   default placeholder
  components/feed/PostCard.tsx  long-press menu (Delete post, confirm,
                             Actions / Cancel)
  components/feed/ShareSheet.tsx  sheet title, contact-search placeholder,
                             empty state, Select contacts / Send button,
                             plural helper rewritten for English
  components/chat/PostRefCard.tsx  "POST" ribbon, "photo" indicator
  lib/api.ts                 humanizeTxError (rate-limit, clock skew,
                             bad signature, 400/5xx/network-error
                             messages)
  lib/dates.ts               dateBucket now returns Today/Yesterday/
                             "Jun 17, 2025"; month array switched to
                             English short forms

Code comments left in Russian intentionally — they're developer
context, not user-facing. This commit is purely display-string.

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

client-app/app/(app)/feed/[id].tsx

@@ -79,7 +79,7 @@ export default function PostDetailScreen() {
       <Header
         divider
         left={<IconButton icon="chevron-back" size={36} onPress={() => router.back()} />}
-        title="Пост"
+        title="Post"
       />
 
       {loading ? (
@@ -94,7 +94,7 @@ export default function PostDetailScreen() {
         <View style={{ padding: 24, alignItems: 'center' }}>
           <Ionicons name="trash-outline" size={32} color="#6a6a6a" />
           <Text style={{ color: '#8b8b8b', marginTop: 10 }}>
-            Пост удалён или больше недоступен
+            Post deleted or no longer available
           </Text>
         </View>
       ) : (
@@ -131,18 +131,18 @@ export default function PostDetailScreen() {
               textTransform: 'uppercase',
               marginBottom: 10,
             }}>
-              Информация о посте
+              Post details
             </Text>
 
-            <DetailRow label="Просмотров" value={formatCount(stats?.views ?? post.views)} />
-            <DetailRow label="Лайков"     value={formatCount(stats?.likes ?? post.likes)} />
-            <DetailRow label="Размер"     value={`${Math.round(post.size / 1024 * 10) / 10} KB`} />
+            <DetailRow label="Views" value={formatCount(stats?.views ?? post.views)} />
+            <DetailRow label="Likes" value={formatCount(stats?.likes ?? post.likes)} />
+            <DetailRow label="Size"  value={`${Math.round(post.size / 1024 * 10) / 10} KB`} />
             <DetailRow
-              label="Стоимость публикации"
+              label="Paid to publish"
               value={formatFee(1000 + post.size)}
             />
             <DetailRow
-              label="Хостинг"
+              label="Hosted on"
               value={shortAddr(post.hosting_relay)}
               mono
             />
@@ -151,7 +151,7 @@ export default function PostDetailScreen() {
               <>
                 <View style={{ height: 1, backgroundColor: '#1f1f1f', marginVertical: 10 }} />
                 <Text style={{ color: '#5a5a5a', fontSize: 11, marginBottom: 6 }}>
-                  Хештеги
+                  Hashtags
                 </Text>
                 <View style={{ flexDirection: 'row', flexWrap: 'wrap', gap: 6 }}>
                   {post.hashtags.map(tag => (