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/chat/rows.ts

@@ -0,0 +1,79 @@
+/**
+ * Группировка сообщений в rows для FlatList чат-экрана.
+ *
+ * Чистая функция — никаких React-зависимостей, легко тестируется unit'ом.
+ *
+ * Правила:
+ *   1. Между разными календарными днями вставляется {kind:'sep', label}.
+ *   2. Внутри одного дня peer-сообщения группируются в "лесенку" с учётом:
+ *        - смены отправителя
+ *        - перерыва > 1 часа между соседними сообщениями
+ *      В пределах одной группы:
+ *        showName   = true   только у первого
+ *        showAvatar = true   только у последнего
+ *   3. mine-сообщения всегда idle: showName=false, showAvatar=false
+ *      (в референсе X-style никогда не рисуется имя/аватар над своим bubble).
+ *
+ * showName/showAvatar всё равно вычисляются — даже если потом render-слой
+ * их проигнорирует (DM / channel — без sender-meta). Логика кнопки renders
+ * сама решает показывать ли их, см. MessageBubble → withSenderMeta.
+ */
+import type { Message } from '@/lib/types';
+import { dateBucket } from '@/lib/dates';
+
+export type Row =
+  | { kind: 'sep'; id: string; label: string }
+  | {
+      kind:       'msg';
+      msg:        Message;
+      showName:   boolean;
+      showAvatar: boolean;
+    };
+
+// Максимальная пауза внутри "лесенки" — после неё новый run.
+const RUN_GAP_SECONDS = 60 * 60; // 1 час
+
+export function buildRows(msgs: Message[]): Row[] {
+  const out: Row[] = [];
+  let lastBucket = '';
+
+  for (let i = 0; i < msgs.length; i++) {
+    const m = msgs[i];
+    const b = dateBucket(m.timestamp);
+
+    if (b !== lastBucket) {
+      out.push({ kind: 'sep', id: `sep_${b}_${m.id}`, label: b });
+      lastBucket = b;
+    }
+
+    const prev = msgs[i - 1];
+    const next = msgs[i + 1];
+
+    // "Прервать run" флаги:
+    //   - разный день
+    //   - разный отправитель
+    //   - своё vs чужое
+    //   - пауза > 1 часа
+    const breakBefore =
+      !prev ||
+      dateBucket(prev.timestamp) !== b ||
+      prev.from !== m.from ||
+      prev.mine !== m.mine ||
+      (m.timestamp - prev.timestamp) > RUN_GAP_SECONDS;
+
+    const breakAfter =
+      !next ||
+      dateBucket(next.timestamp) !== b ||
+      next.from !== m.from ||
+      next.mine !== m.mine ||
+      (next.timestamp - m.timestamp) > RUN_GAP_SECONDS;
+
+    // Для mine — никогда не показываем имя/аватар.
+    const showName   = m.mine ? false : breakBefore;
+    const showAvatar = m.mine ? false : breakAfter;
+
+    out.push({ kind: 'msg', msg: m, showName, showAvatar });
+  }
+
+  return out;
+}