feat(client): Twitter-style social feed UI (Phase C of v2.0.0)

Ships the client side of the v2.0.0 feed feature. Folds client-app/
into the monorepo (was previously .gitignored as "tracked separately"
but no separate repo ever existed — for v2.0.0 the client is
first-class).

Feed screens

  app/(app)/feed.tsx — Feed tab
    - Three-way tab strip: Подписки / Для вас / В тренде backed by
      /feed/timeline, /feed/foryou, /feed/trending respectively
    - Default landing tab is "Для вас" — surfaces discovery without
      requiring the user to follow anyone first
    - FlatList with pull-to-refresh + viewability-driven view counter
      bump (posts visible ≥ 60% for ≥ 1s trigger POST /feed/post/…/view)
    - Floating blue compose button → /compose
    - Per-post liked_by_me fetched in batches of 6 after list load

  app/(app)/compose.tsx — post composer modal
    - Fullscreen, Twitter-like header (✕ left, Опубликовать right)
    - Auto-focused multiline TextInput, 4000 char cap
    - Hashtag preview chips that auto-update as you type
    - expo-image-picker + expo-image-manipulator pipeline: resize to
      1080px max-dim, JPEG Q=50 (client-side first-pass compression
      before the mandatory server-side scrub)
    - Live fee estimate + balance guard with a confirmation modal
      ("Опубликовать пост? Цена: 0.00X T · Размер: N KB")
    - Exif: false passed to ImagePicker as an extra privacy layer

  app/(app)/feed/[id].tsx — post detail
    - Full PostCard rendering + detailed info panel (views, likes,
      size, fee, hosting relay, hashtags as tappable chips)
    - Triggers bumpView on mount
    - 410 (on-chain soft-delete) routes back to the feed

  app/(app)/feed/tag/[tag].tsx — hashtag feed

  app/(app)/profile/[address].tsx — rebuilt
    - Twitter-ish profile: avatar, name, address short-form, post count
    - Posts | Инфо tab strip
    - Follow / Unfollow button for non-self profiles (optimistic UI)
    - Edit button on self profile → settings
    - Secondary actions (chat, copy address) when viewing a known contact

Supporting library

  lib/feed.ts — HTTP wrappers + tx builders for every /feed/* endpoint:
    - publishPost (POST /feed/publish, signed)
    - publishAndCommit (publish → on-chain CREATE_POST)
    - fetchPost / fetchStats / bumpView
    - fetchAuthorPosts / fetchTimeline / fetchForYou / fetchTrending /
      fetchHashtag
    - buildCreatePostTx / buildDeletePostTx
    - buildFollowTx / buildUnfollowTx
    - buildLikePostTx / buildUnlikePostTx
    - likePost / unlikePost / followUser / unfollowUser / deletePost
      (high-level helpers that bundle build + submitTx)
    - formatFee, formatRelativeTime, formatCount — Twitter-like display
      helpers

  components/feed/PostCard.tsx — core card component
    - Memoised for performance (N-row re-render on every like elsewhere
      would cost a lot otherwise)
    - Optimistic like toggle with heart-bounce spring animation
    - Hashtag highlighting in body text (tappable → hashtag feed)
    - Long-press context menu (Delete, owner-only)
    - Views / likes / share-link / reply icons in footer row

Navigation cleanup

  - NavBar: removed the SOON pill on the Feed tab (it's shipped now)
  - (app)/_layout: hide NavBar on /compose and /feed/* sub-routes
  - AnimatedSlot: treat /feed/<id>, /feed/tag/<t>, /compose as
    sub-routes so back-swipe-right closes them

Channel removal (client side)

  - lib/types.ts: ContactKind stripped to 'direct' | 'group'; legacy
    'channel' flag removed. `kind` field kept for backward compat with
    existing AsyncStorage records.
  - lib/devSeed.ts: dropped the 5 channel seed contacts.
  - components/ChatTile.tsx: removed channel kindIcon branch.

Dependencies

  - expo-image-manipulator added for client-side image compression.
  - expo-file-system/legacy used for readAsStringAsync (SDK 54 moved
    that API to the legacy sub-path; the new streaming API isn't yet
    stable).

Type check

  - npx tsc --noEmit — clean, 0 errors.

Next (not in this commit)

  - Direct attachment-bytes endpoint on the server so post-detail can
    actually render the image (currently shows placeholder with URL)
  - Cross-relay body fetch via /api/relays + hosting_relay pubkey
  - Mentions (@username) with notifications
  - Full-text search

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

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

@@ -0,0 +1,242 @@
+/**
+ * Post detail — full view of one post with stats, thread context, and a
+ * lazy-rendered image attachment.
+ *
+ * Why a dedicated screen?
+ *  - PostCard in the timeline intentionally doesn't render attachments
+ *    (would explode initial render time with N images).
+ *  - Per-post stats (views, likes, liked_by_me) want a fresh refresh
+ *    on open; timeline batches but not at the per-second cadence a
+ *    reader expects when they just tapped in.
+ *
+ * Layout:
+ *   [← back  ·  Пост]
+ *   [PostCard (full — with attachment)]
+ *   [stats bar: views · likes · fee]
+ *   [— reply affordance below (future)]
+ */
+import React, { useCallback, useEffect, useState } from 'react';
+import {
+  View, Text, ScrollView, ActivityIndicator, Image,
+} from 'react-native';
+import { Ionicons } from '@expo/vector-icons';
+import { router, useLocalSearchParams } from 'expo-router';
+
+import { Header } from '@/components/Header';
+import { IconButton } from '@/components/IconButton';
+import { PostCard } from '@/components/feed/PostCard';
+import { useStore } from '@/lib/store';
+import {
+  fetchPost, fetchStats, bumpView, formatCount, formatFee,
+  type FeedPostItem, type PostStats,
+} from '@/lib/feed';
+
+export default function PostDetailScreen() {
+  const { id: postID } = useLocalSearchParams<{ id: string }>();
+  const keyFile = useStore(s => s.keyFile);
+
+  const [post, setPost]   = useState<FeedPostItem | null>(null);
+  const [stats, setStats] = useState<PostStats | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+
+  const load = useCallback(async () => {
+    if (!postID) return;
+    setLoading(true);
+    setError(null);
+    try {
+      const [p, s] = await Promise.all([
+        fetchPost(postID),
+        fetchStats(postID, keyFile?.pub_key),
+      ]);
+      setPost(p);
+      setStats(s);
+      if (p) bumpView(postID);  // fire-and-forget
+    } catch (e: any) {
+      setError(String(e?.message ?? e));
+    } finally {
+      setLoading(false);
+    }
+  }, [postID, keyFile]);
+
+  useEffect(() => { load(); }, [load]);
+
+  const onStatsChanged = useCallback(async () => {
+    if (!postID) return;
+    const s = await fetchStats(postID, keyFile?.pub_key);
+    if (s) setStats(s);
+  }, [postID, keyFile]);
+
+  const onDeleted = useCallback(() => {
+    // Go back to feed — the post is gone.
+    router.back();
+  }, []);
+
+  return (
+    <View style={{ flex: 1, backgroundColor: '#000000' }}>
+      <Header
+        divider
+        left={<IconButton icon="chevron-back" size={36} onPress={() => router.back()} />}
+        title="Пост"
+      />
+
+      {loading ? (
+        <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
+          <ActivityIndicator color="#1d9bf0" />
+        </View>
+      ) : error ? (
+        <View style={{ padding: 24 }}>
+          <Text style={{ color: '#f4212e' }}>{error}</Text>
+        </View>
+      ) : !post ? (
+        <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
+          </Text>
+        </View>
+      ) : (
+        <ScrollView>
+          <PostCard
+            post={{ ...post, likes: stats?.likes ?? post.likes, views: stats?.views ?? post.views }}
+            likedByMe={stats?.liked_by_me ?? false}
+            onStatsChanged={onStatsChanged}
+            onDeleted={onDeleted}
+          />
+
+          {/* Attachment preview (if any). For MVP we try loading from the
+              CURRENT node — works when you're connected to the hosting
+              relay. Cross-relay discovery (look up hosting_relay URL via
+              /api/relays) is future work. */}
+          {post.has_attachment && (
+            <AttachmentPreview postID={post.post_id} />
+          )}
+
+          {/* Detailed stats block */}
+          <View
+            style={{
+              marginHorizontal: 14,
+              marginTop: 12,
+              paddingVertical: 14,
+              paddingHorizontal: 14,
+              borderRadius: 14,
+              backgroundColor: '#0a0a0a',
+              borderWidth: 1,
+              borderColor: '#1f1f1f',
+            }}
+          >
+            <Text style={{
+              color: '#5a5a5a',
+              fontSize: 11,
+              fontWeight: '700',
+              letterSpacing: 1.2,
+              textTransform: 'uppercase',
+              marginBottom: 10,
+            }}>
+              Информация о посте
+            </Text>
+
+            <DetailRow label="Просмотров" value={formatCount(stats?.views ?? post.views)} />
+            <DetailRow label="Лайков"     value={formatCount(stats?.likes ?? post.likes)} />
+            <DetailRow label="Размер"     value={`${Math.round(post.size / 1024 * 10) / 10} KB`} />
+            <DetailRow
+              label="Стоимость публикации"
+              value={formatFee(1000 + post.size)}
+            />
+            <DetailRow
+              label="Хостинг"
+              value={shortAddr(post.hosting_relay)}
+              mono
+            />
+
+            {post.hashtags && post.hashtags.length > 0 && (
+              <>
+                <View style={{ height: 1, backgroundColor: '#1f1f1f', marginVertical: 10 }} />
+                <Text style={{ color: '#5a5a5a', fontSize: 11, marginBottom: 6 }}>
+                  Хештеги
+                </Text>
+                <View style={{ flexDirection: 'row', flexWrap: 'wrap', gap: 6 }}>
+                  {post.hashtags.map(tag => (
+                    <Text
+                      key={tag}
+                      onPress={() => router.push(`/(app)/feed/tag/${encodeURIComponent(tag)}` as never)}
+                      style={{
+                        color: '#1d9bf0',
+                        fontSize: 13,
+                        paddingHorizontal: 8,
+                        paddingVertical: 3,
+                        backgroundColor: '#081a2a',
+                        borderRadius: 999,
+                      }}
+                    >
+                      #{tag}
+                    </Text>
+                  ))}
+                </View>
+              </>
+            )}
+          </View>
+
+          <View style={{ height: 80 }} />
+        </ScrollView>
+      )}
+    </View>
+  );
+}
+
+function DetailRow({ label, value, mono }: { label: string; value: string; mono?: boolean }) {
+  return (
+    <View style={{ flexDirection: 'row', paddingVertical: 3 }}>
+      <Text style={{ color: '#8b8b8b', fontSize: 13, flex: 1 }}>{label}</Text>
+      <Text
+        style={{
+          color: '#ffffff',
+          fontSize: 13,
+          fontWeight: '600',
+          fontFamily: mono ? 'monospace' : undefined,
+        }}
+      >
+        {value}
+      </Text>
+    </View>
+  );
+}
+
+function AttachmentPreview({ postID }: { postID: string }) {
+  // For MVP we hit the local node URL; if the body is hosted elsewhere
+  // the image load will fail and the placeholder stays visible.
+  const { getNodeUrl } = require('@/lib/api');
+  const url = `${getNodeUrl()}/feed/post/${postID}`;
+  // The body is a JSON object, not raw image bytes. For now we just
+  // show a placeholder — decoding base64 attachment → data-uri is a
+  // Phase D improvement once we add /feed/post/{id}/attachment raw bytes.
+  return (
+    <View
+      style={{
+        margin: 14,
+        paddingVertical: 32,
+        borderRadius: 14,
+        backgroundColor: '#0a0a0a',
+        borderWidth: 1,
+        borderColor: '#1f1f1f',
+        alignItems: 'center',
+      }}
+    >
+      <Ionicons name="image-outline" size={32} color="#5a5a5a" />
+      <Text style={{ color: '#8b8b8b', marginTop: 10, fontSize: 12 }}>
+        Вложение: {url}
+      </Text>
+      <Text style={{ color: '#5a5a5a', marginTop: 4, fontSize: 10 }}>
+        Прямой просмотр вложений — в следующем релизе
+      </Text>
+    </View>
+  );
+}
+
+function shortAddr(a: string, n = 6): string {
+  if (!a) return '—';
+  return a.length <= n * 2 + 1 ? a : `${a.slice(0, n)}…${a.slice(-n)}`;
+}
+
+// Silence Image import when unused (reserved for future attachment preview).
+void Image;