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)/profile/[address].tsx

@@ -48,7 +48,7 @@ export default function ProfileScreen() {
   const isMe = !!keyFile && keyFile.pub_key === address;
   const displayName = contact?.username
     ? `@${contact.username}`
-    : contact?.alias ?? (isMe ? 'Вы' : shortAddr(address ?? '', 6));
+    : contact?.alias ?? (isMe ? 'You' : shortAddr(address ?? '', 6));
 
   const copyAddress = async () => {
     if (!address) return;
@@ -85,7 +85,7 @@ export default function ProfileScreen() {
   return (
     <View style={{ flex: 1, backgroundColor: '#000000', paddingTop: insets.top }}>
       <Header
-        title="Профиль"
+        title="Profile"
         divider
         left={<IconButton icon="chevron-back" size={36} onPress={() => router.back()} />}
       />
@@ -124,7 +124,7 @@ export default function ProfileScreen() {
                     fontSize: 13,
                   }}
                 >
-                  {following ? 'Вы подписаны' : 'Подписаться'}
+                  {following ? 'Following' : 'Follow'}
                 </Text>
               )}
             </Pressable>
@@ -139,7 +139,7 @@ export default function ProfileScreen() {
               })}
             >
               <Text style={{ color: '#ffffff', fontWeight: '700', fontSize: 13 }}>
-                Редактировать
+                Edit
               </Text>
             </Pressable>
           )}
@@ -177,7 +177,7 @@ export default function ProfileScreen() {
           >
             <Ionicons name="chatbubble-outline" size={15} color="#ffffff" />
             <Text style={{ color: '#ffffff', fontWeight: '600', fontSize: 14 }}>
-              Открыть чат
+              Open chat
             </Text>
           </Pressable>
         )}
@@ -203,7 +203,7 @@ export default function ProfileScreen() {
             })}
           >
             <Text style={{ color: '#8b8b8b', fontSize: 13, flex: 1 }}>
-              Адрес
+              Address
             </Text>
             <Text
               style={{
@@ -214,7 +214,7 @@ export default function ProfileScreen() {
               }}
               numberOfLines={1}
             >
-              {copied ? 'Скопировано' : shortAddr(address ?? '')}
+              {copied ? 'Copied' : shortAddr(address ?? '')}
             </Text>
             <Ionicons
               name={copied ? 'checkmark' : 'copy-outline'}
@@ -229,17 +229,17 @@ export default function ProfileScreen() {
             <>
               <Divider />
               <InfoRow
-                label="Шифрование"
+                label="Encryption"
                 value={contact.x25519Pub
                   ? 'end-to-end (NaCl)'
-                  : 'ключ ещё не опубликован'}
+                  : 'key not published yet'}
                 danger={!contact.x25519Pub}
                 icon={contact.x25519Pub ? 'lock-closed' : 'lock-open'}
               />
 
               <Divider />
               <InfoRow
-                label="Добавлен"
+                label="Added"
                 value={new Date(contact.addedAt).toLocaleDateString()}
                 icon="calendar-outline"
               />
@@ -251,7 +251,7 @@ export default function ProfileScreen() {
                 <>
                   <Divider />
                   <InfoRow
-                    label="Участников"
+                    label="Members"
                     value="—"
                     icon="people-outline"
                   />
@@ -270,7 +270,7 @@ export default function ProfileScreen() {
             paddingHorizontal: 24,
             lineHeight: 17,
           }}>
-            Этот пользователь пока не в ваших контактах. Нажмите «Подписаться», чтобы видеть его посты в ленте, или добавьте в чаты через @username.
+            This user isn't in your contacts yet. Tap "Follow" to see their posts in your feed, or add them as a chat contact via @username.
           </Text>
         )}
       </ScrollView>