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)/compose.tsx

@@ -98,11 +98,11 @@ export default function ComposeScreen() {
       const perm = await ImagePicker.requestMediaLibraryPermissionsAsync();
       if (!perm.granted) {
         Alert.alert(
-          'Нужен доступ к фото',
-          'Откройте настройки и разрешите доступ к галерее.',
+          'Photo access required',
+          'Please enable photo library access in Settings.',
           [
-            { text: 'Отмена' },
-            { text: 'Настройки', onPress: () => Linking.openSettings() },
+            { text: 'Cancel' },
+            { text: 'Settings', onPress: () => Linking.openSettings() },
           ],
         );
         return;
@@ -132,8 +132,8 @@ export default function ComposeScreen() {
 
       if (bytes.length > MAX_POST_BYTES - 512) {
         Alert.alert(
-          'Слишком большое',
-          `Картинка ${Math.round(bytes.length / 1024)} KB — лимит ${MAX_POST_BYTES / 1024} KB. Попробуйте выбрать поменьше.`,
+          'Image too large',
+          `Image is ${Math.round(bytes.length / 1024)} KB but the limit is ${MAX_POST_BYTES / 1024} KB. Try picking a smaller one.`,
         );
         return;
       }
@@ -147,7 +147,7 @@ export default function ComposeScreen() {
         height: manipulated.height,
       });
     } catch (e: any) {
-      Alert.alert('Не удалось', String(e?.message ?? e));
+      Alert.alert('Failed', String(e?.message ?? e));
     } finally {
       setPicking(false);
     }
@@ -159,19 +159,19 @@ export default function ComposeScreen() {
     // Balance guard.
     if (balance !== null && balance < estimatedFee) {
       Alert.alert(
-        'Недостаточно средств',
-        `Нужно ${formatFee(estimatedFee)}, на балансе ${formatFee(balance)}.`,
+        'Insufficient balance',
+        `Need ${formatFee(estimatedFee)}, have ${formatFee(balance)}.`,
       );
       return;
     }
 
     Alert.alert(
-      'Опубликовать пост?',
-      `Цена: ${formatFee(estimatedFee)}\nРазмер: ${Math.round(totalBytes / 1024 * 10) / 10} KB`,
+      'Publish post?',
+      `Cost: ${formatFee(estimatedFee)}\nSize: ${Math.round(totalBytes / 1024 * 10) / 10} KB`,
       [
-        { text: 'Отмена', style: 'cancel' },
+        { text: 'Cancel', style: 'cancel' },
         {
-          text: 'Опубликовать',
+          text: 'Publish',
           onPress: async () => {
             setBusy(true);
             try {
@@ -185,7 +185,7 @@ export default function ComposeScreen() {
               // Close composer and open the new post.
               router.replace(`/(app)/feed/${postID}` as never);
             } catch (e: any) {
-              Alert.alert('Не удалось опубликовать', humanizeTxError(e));
+              Alert.alert('Failed to publish', humanizeTxError(e));
             } finally {
               setBusy(false);
             }
@@ -235,7 +235,7 @@ export default function ComposeScreen() {
                 fontSize: 14,
               }}
             >
-              Опубликовать
+              Publish
             </Text>
           )}
         </Pressable>
@@ -251,7 +251,7 @@ export default function ComposeScreen() {
           <TextInput
             value={content}
             onChangeText={setContent}
-            placeholder="Что происходит?"
+            placeholder="What's happening?"
             placeholderTextColor="#5a5a5a"
             multiline
             maxLength={MAX_CONTENT_LENGTH}
@@ -328,7 +328,7 @@ export default function ComposeScreen() {
               </Pressable>
             </View>
             <Text style={{ color: '#6a6a6a', fontSize: 11, marginTop: 6 }}>
-              {Math.round(attach.size / 1024)} KB · метаданные удалят на сервере
+              {Math.round(attach.size / 1024)} KB · metadata stripped on server
             </Text>
           </View>
         )}