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/lib/store.ts

@@ -0,0 +1,128 @@
+/**
+ * Global app state via Zustand.
+ * Keeps runtime state; persistent data lives in storage.ts.
+ */
+
+import { create } from 'zustand';
+import type { KeyFile, Contact, Chat, Message, ContactRequest, NodeSettings } from './types';
+
+interface AppState {
+  // Identity
+  keyFile:    KeyFile | null;
+  username:   string | null;
+  setKeyFile: (kf: KeyFile | null) => void;
+  setUsername: (u: string | null) => void;
+
+  // Node settings
+  settings:     NodeSettings;
+  setSettings:  (s: Partial<NodeSettings>) => void;
+
+  // Contacts
+  contacts:    Contact[];
+  setContacts: (contacts: Contact[]) => void;
+  upsertContact: (c: Contact) => void;
+
+  // Chats (derived from contacts + messages)
+  chats:    Chat[];
+  setChats: (chats: Chat[]) => void;
+
+  // Active chat messages
+  messages:    Record<string, Message[]>;  // key: contactAddress
+  setMessages: (chatId: string, msgs: Message[]) => void;
+  appendMessage: (chatId: string, msg: Message) => void;
+
+  // Contact requests (pending)
+  requests:    ContactRequest[];
+  setRequests: (reqs: ContactRequest[]) => void;
+
+  // Balance
+  balance:    number;
+  setBalance: (b: number) => void;
+
+  // Loading / error states
+  loading:  boolean;
+  setLoading: (v: boolean) => void;
+  error:    string | null;
+  setError: (e: string | null) => void;
+
+  // Nonce cache (to avoid refetching)
+  nonce:    number;
+  setNonce: (n: number) => void;
+
+  // Per-contact unread counter (reset on chat open, bumped on peer msg arrive).
+  // Keyed by contactAddress (Ed25519 pubkey hex).
+  unreadByContact:   Record<string, number>;
+  incrementUnread:   (contactAddress: string) => void;
+  clearUnread:       (contactAddress: string) => void;
+  /** Bootstrap state: `true` after initial loadKeyFile + loadSettings done. */
+  booted:            boolean;
+  setBooted:         (b: boolean) => void;
+}
+
+export const useStore = create<AppState>((set, get) => ({
+  keyFile:    null,
+  username:   null,
+  setKeyFile: (kf) => set({ keyFile: kf }),
+  setUsername: (u) => set({ username: u }),
+
+  settings: {
+    nodeUrl:    'http://localhost:8081',
+    contractId: '',
+  },
+  setSettings: (s) => set(state => ({ settings: { ...state.settings, ...s } })),
+
+  contacts:    [],
+  setContacts: (contacts) => set({ contacts }),
+  upsertContact: (c) => set(state => {
+    const idx = state.contacts.findIndex(x => x.address === c.address);
+    if (idx >= 0) {
+      const updated = [...state.contacts];
+      updated[idx] = c;
+      return { contacts: updated };
+    }
+    return { contacts: [...state.contacts, c] };
+  }),
+
+  chats:    [],
+  setChats: (chats) => set({ chats }),
+
+  messages:    {},
+  setMessages: (chatId, msgs) => set(state => ({
+    messages: { ...state.messages, [chatId]: msgs },
+  })),
+  appendMessage: (chatId, msg) => set(state => {
+    const current = state.messages[chatId] ?? [];
+    if (current.find(m => m.id === msg.id)) return {};
+    return { messages: { ...state.messages, [chatId]: [...current, msg] } };
+  }),
+
+  requests:    [],
+  setRequests: (reqs) => set({ requests: reqs }),
+
+  balance:    0,
+  setBalance: (b) => set({ balance: b }),
+
+  loading:    false,
+  setLoading: (v) => set({ loading: v }),
+  error:      null,
+  setError:   (e) => set({ error: e }),
+
+  nonce:    0,
+  setNonce: (n) => set({ nonce: n }),
+
+  unreadByContact: {},
+  incrementUnread: (addr) => set(state => ({
+    unreadByContact: {
+      ...state.unreadByContact,
+      [addr]: (state.unreadByContact[addr] ?? 0) + 1,
+    },
+  })),
+  clearUnread: (addr) => set(state => {
+    if (!state.unreadByContact[addr]) return {};
+    const next = { ...state.unreadByContact };
+    delete next[addr];
+    return { unreadByContact: next };
+  }),
+  booted:    false,
+  setBooted: (b) => set({ booted: b }),
+}));