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/components/Avatar.tsx

@@ -0,0 +1,76 @@
+/**
+ * Avatar — круглая заглушка с инициалом, опционально online-пип.
+ * Нет зависимостей от асинхронных источников (картинок) — для messenger-тайла
+ * важнее мгновенный рендер, чем фотография. Если в будущем будут фото,
+ * расширяем здесь.
+ */
+import React from 'react';
+import { View, Text } from 'react-native';
+
+export interface AvatarProps {
+  /** Имя / @username — берём первый символ для placeholder. */
+  name?: string;
+  /** Адрес (hex pubkey) — fallback для тех у кого нет имени. */
+  address?: string;
+  /** Общий размер в px. По умолчанию 48 (tile size). */
+  size?: number;
+  /** Цвет пипа справа-снизу. undefined = без пипа. */
+  dotColor?: string;
+  /** Класс для обёртки (position: relative кадр). */
+  className?: string;
+}
+
+/** Простое хэширование имени → один из 6 оттенков серого для разнообразия. */
+function pickBg(seed: string): string {
+  const shades = ['#1a1a1a', '#222222', '#2a2a2a', '#151515', '#1c1c1c', '#1f1f1f'];
+  let h = 0;
+  for (let i = 0; i < seed.length; i++) h = (h * 31 + seed.charCodeAt(i)) & 0xffff;
+  return shades[h % shades.length];
+}
+
+export function Avatar({ name, address, size = 48, dotColor, className }: AvatarProps) {
+  const seed = (name ?? address ?? '?').replace(/^@/, '');
+  const initial = seed.charAt(0).toUpperCase() || '?';
+  const bg = pickBg(seed);
+
+  return (
+    <View className={className} style={{ width: size, height: size, position: 'relative' }}>
+      <View
+        style={{
+          width: size,
+          height: size,
+          borderRadius: size / 2,
+          backgroundColor: bg,
+          alignItems: 'center',
+          justifyContent: 'center',
+        }}
+      >
+        <Text
+          style={{
+            color: '#d0d0d0',
+            fontSize: size * 0.4,
+            fontWeight: '600',
+            includeFontPadding: false,
+          }}
+        >
+          {initial}
+        </Text>
+      </View>
+      {dotColor && (
+        <View
+          style={{
+            position: 'absolute',
+            right: 0,
+            bottom: 0,
+            width: size * 0.28,
+            height: size * 0.28,
+            borderRadius: size * 0.14,
+            backgroundColor: dotColor,
+            borderWidth: 2,
+            borderColor: '#000',
+          }}
+        />
+      )}
+    </View>
+  );
+}