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)/requests.tsx

@@ -51,7 +51,7 @@ export default function RequestsScreen() {
       setRequests(requests.filter(r => r.txHash !== req.txHash));
       router.replace(`/(app)/chats/${req.from}` as never);
     } catch (e: any) {
-      Alert.alert('Не удалось принять', humanizeTxError(e));
+      Alert.alert('Accept failed', humanizeTxError(e));
     } finally {
       setAccepting(null);
     }
@@ -59,12 +59,12 @@ export default function RequestsScreen() {
 
   function decline(req: ContactRequest) {
     Alert.alert(
-      'Отклонить запрос',
-      `Отклонить запрос от ${req.username ? '@' + req.username : shortAddr(req.from)}?`,
+      'Decline request',
+      `Decline request from ${req.username ? '@' + req.username : shortAddr(req.from)}?`,
       [
-        { text: 'Отмена', style: 'cancel' },
+        { text: 'Cancel', style: 'cancel' },
         {
-          text: 'Отклонить',
+          text: 'Decline',
           style: 'destructive',
           onPress: () => setRequests(requests.filter(r => r.txHash !== req.txHash)),
         },
@@ -91,7 +91,7 @@ export default function RequestsScreen() {
             {name}
           </Text>
           <Text style={{ color: '#8b8b8b', fontSize: 12, marginTop: 2 }}>
-            хочет добавить вас в контакты · {relativeTime(req.timestamp)}
+            wants to add you as a contact · {relativeTime(req.timestamp)}
           </Text>
           {req.intro ? (
             <Text
@@ -123,7 +123,7 @@ export default function RequestsScreen() {
               {isAccepting ? (
                 <ActivityIndicator size="small" color="#ffffff" />
               ) : (
-                <Text style={{ color: '#ffffff', fontWeight: '700', fontSize: 13 }}>Принять</Text>
+                <Text style={{ color: '#ffffff', fontWeight: '700', fontSize: 13 }}>Accept</Text>
               )}
             </Pressable>
             <Pressable
@@ -137,7 +137,7 @@ export default function RequestsScreen() {
                 borderWidth: 1, borderColor: '#1f1f1f',
               })}
             >
-              <Text style={{ color: '#ffffff', fontWeight: '600', fontSize: 13 }}>Отклонить</Text>
+              <Text style={{ color: '#ffffff', fontWeight: '600', fontSize: 13 }}>Decline</Text>
             </Pressable>
           </View>
         </View>
@@ -147,16 +147,16 @@ export default function RequestsScreen() {
 
   return (
     <View style={{ flex: 1, backgroundColor: '#000000', paddingTop: insets.top }}>
-      <TabHeader title="Уведомления" />
+      <TabHeader title="Notifications" />
 
       {requests.length === 0 ? (
         <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center', paddingHorizontal: 32 }}>
           <Ionicons name="notifications-outline" size={42} color="#3a3a3a" />
           <Text style={{ color: '#ffffff', fontSize: 16, fontWeight: '700', marginTop: 10 }}>
-            Всё прочитано
+            All caught up
           </Text>
           <Text style={{ color: '#8b8b8b', fontSize: 13, textAlign: 'center', marginTop: 6, lineHeight: 19 }}>
-            Запросы на общение и события сети появятся здесь.
+            Contact requests and network events will appear here.
           </Text>
         </View>
       ) : (