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)/requests.tsx

@@ -0,0 +1,173 @@
+/**
+ * Contact requests / notifications — dark minimalist.
+ *
+ * В референсе нижний таб «notifications» ведёт сюда. Пока это только
+ * incoming CONTACT_REQUEST'ы; позже сюда же придут другие системные
+ * уведомления (slash, ADD_VALIDATOR со-sig-ing, и т.д.).
+ */
+import React, { useState } from 'react';
+import { View, Text, FlatList, Alert, Pressable, ActivityIndicator } from 'react-native';
+import { router } from 'expo-router';
+import { Ionicons } from '@expo/vector-icons';
+import { useSafeAreaInsets } from 'react-native-safe-area-context';
+import { useStore } from '@/lib/store';
+import {
+  buildAcceptContactTx, submitTx, getIdentity, humanizeTxError,
+} from '@/lib/api';
+import { saveContact } from '@/lib/storage';
+import { shortAddr } from '@/lib/crypto';
+import { relativeTime } from '@/lib/utils';
+import type { ContactRequest } from '@/lib/types';
+
+import { Avatar } from '@/components/Avatar';
+import { TabHeader } from '@/components/TabHeader';
+import { IconButton } from '@/components/IconButton';
+
+export default function RequestsScreen() {
+  const insets        = useSafeAreaInsets();
+  const keyFile       = useStore(s => s.keyFile);
+  const requests      = useStore(s => s.requests);
+  const setRequests   = useStore(s => s.setRequests);
+  const upsertContact = useStore(s => s.upsertContact);
+
+  const [accepting, setAccepting] = useState<string | null>(null);
+
+  async function accept(req: ContactRequest) {
+    if (!keyFile) return;
+    setAccepting(req.txHash);
+    try {
+      const identity = await getIdentity(req.from);
+      const x25519Pub = identity?.x25519_pub ?? '';
+
+      const tx = buildAcceptContactTx({
+        from: keyFile.pub_key, to: req.from, privKey: keyFile.priv_key,
+      });
+      await submitTx(tx);
+
+      const contact = { address: req.from, x25519Pub, username: req.username, addedAt: Date.now() };
+      upsertContact(contact);
+      await saveContact(contact);
+
+      setRequests(requests.filter(r => r.txHash !== req.txHash));
+      router.replace(`/(app)/chats/${req.from}` as never);
+    } catch (e: any) {
+      Alert.alert('Accept failed', humanizeTxError(e));
+    } finally {
+      setAccepting(null);
+    }
+  }
+
+  function decline(req: ContactRequest) {
+    Alert.alert(
+      'Decline request',
+      `Decline request from ${req.username ? '@' + req.username : shortAddr(req.from)}?`,
+      [
+        { text: 'Cancel', style: 'cancel' },
+        {
+          text: 'Decline',
+          style: 'destructive',
+          onPress: () => setRequests(requests.filter(r => r.txHash !== req.txHash)),
+        },
+      ],
+    );
+  }
+
+  const renderItem = ({ item: req }: { item: ContactRequest }) => {
+    const name = req.username ? `@${req.username}` : shortAddr(req.from);
+    const isAccepting = accepting === req.txHash;
+    return (
+      <View
+        style={{
+          flexDirection: 'row',
+          paddingHorizontal: 14,
+          paddingVertical: 12,
+          borderBottomWidth: 1,
+          borderBottomColor: '#0f0f0f',
+        }}
+      >
+        <Avatar name={name} address={req.from} size={44} />
+        <View style={{ flex: 1, marginLeft: 12, minWidth: 0 }}>
+          <Text style={{ color: '#ffffff', fontWeight: '700', fontSize: 15 }}>
+            {name}
+          </Text>
+          <Text style={{ color: '#8b8b8b', fontSize: 12, marginTop: 2 }}>
+            wants to message you · {relativeTime(req.timestamp)}
+          </Text>
+          {req.intro ? (
+            <Text
+              style={{
+                color: '#d0d0d0', fontSize: 13, lineHeight: 18,
+                marginTop: 6,
+                padding: 8,
+                borderRadius: 10,
+                backgroundColor: '#0a0a0a',
+                borderWidth: 1, borderColor: '#1f1f1f',
+              }}
+              numberOfLines={3}
+            >
+              {req.intro}
+            </Text>
+          ) : null}
+
+          <View style={{ flexDirection: 'row', gap: 8, marginTop: 10 }}>
+            <Pressable
+              onPress={() => accept(req)}
+              disabled={isAccepting}
+              style={({ pressed }) => ({
+                flex: 1,
+                alignItems: 'center', justifyContent: 'center',
+                paddingVertical: 9, borderRadius: 999,
+                backgroundColor: isAccepting ? '#1a1a1a' : pressed ? '#1a8cd8' : '#1d9bf0',
+              })}
+            >
+              {isAccepting ? (
+                <ActivityIndicator size="small" color="#ffffff" />
+              ) : (
+                <Text style={{ color: '#ffffff', fontWeight: '700', fontSize: 13 }}>Accept</Text>
+              )}
+            </Pressable>
+            <Pressable
+              onPress={() => decline(req)}
+              disabled={isAccepting}
+              style={({ pressed }) => ({
+                flex: 1,
+                alignItems: 'center', justifyContent: 'center',
+                paddingVertical: 9, borderRadius: 999,
+                backgroundColor: pressed ? '#1a1a1a' : '#111111',
+                borderWidth: 1, borderColor: '#1f1f1f',
+              })}
+            >
+              <Text style={{ color: '#ffffff', fontWeight: '600', fontSize: 13 }}>Decline</Text>
+            </Pressable>
+          </View>
+        </View>
+      </View>
+    );
+  };
+
+  return (
+    <View style={{ flex: 1, backgroundColor: '#000000', paddingTop: insets.top }}>
+      <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 }}>
+            All caught up
+          </Text>
+          <Text style={{ color: '#8b8b8b', fontSize: 13, textAlign: 'center', marginTop: 6, lineHeight: 19 }}>
+            Contact requests and network events will appear here.
+          </Text>
+        </View>
+      ) : (
+        <FlatList
+          data={requests}
+          keyExtractor={r => r.txHash}
+          renderItem={renderItem}
+          contentContainerStyle={{ paddingBottom: 120 }}
+          showsVerticalScrollIndicator={false}
+        />
+      )}
+    </View>
+  );
+}