feat(feed): image previews + inline header + 5-line truncation + drop comments

Server
  node/api_feed.go: new GET /feed/post/{id}/attachment route. Returns
  raw attachment bytes with the correct Content-Type so React Native's
  <Image source={uri}> can stream them directly without the client
  fetching + decoding base64 from the main /feed/post/{id} JSON (would
  blow up memory on a 40-post timeline). Respects on-chain soft-delete
  (410 when tombstoned). Cache-Control: public, max-age=3600, immutable
  — attachments are content-addressed so aggressive caching is safe.

PostCard — rewritten header row
  - Avatar + name + time collapsed into a single Pressable row with
    flexDirection:'row'. Name gets flexShrink:1 + numberOfLines:1 so
    long handles truncate with "…" mid-row instead of pushing the time
    onto a second line. Time and separator dot both numberOfLines:1
    with no flex — they never shrink, so "2h" stays readable.
  - Whole header is one tap target → navigates to the author's profile.

PostCard — body truncation
  - Timeline view (compact=false): numberOfLines={5} + ellipsizeMode:
    'tail'. Long posts collapse to 5 lines with "…"; tapping the card
    opens the detail view where the full body is shown.
  - Detail view (compact=true): no line cap — full text, then full-
    size attachment below.

PostCard — real image previews
  - <Image source={{ uri: `${node}/feed/post/${id}/attachment` }}>
    (feed layout).
  - Timeline: aspectRatio: 4/5 + resizeMode:'cover' — portrait photos
    get cropped so one tall image can't eat the whole feed.
  - Detail: aspectRatio: 1 + resizeMode:'contain' so the full image
    fits in its original proportions (crop-free).

PostCard — comments button removed
  v2.0.0 doesn't implement replies; a dead button with label "0" was
  noise. Action row now has 3 cells: heart (with live like count),
  eye (views), share (pinned right). Spacing stays balanced because
  each of the first two cells is still flex:1.

Post detail screen
  - Passes compact prop so the PostCard above renders in full-body /
    full-attachment mode.
  - Dropped the old AttachmentPreview placeholder — PostCard now
    handles images in both modes.

Tests
  - go test ./... — all 7 packages green (blockchain / consensus /
    identity / media / node / relay / vm).
  - tsc --noEmit on client-app — 0 errors.

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

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

@@ -17,7 +17,7 @@
  */
 import React, { useCallback, useEffect, useState } from 'react';
 import {
-  View, Text, ScrollView, ActivityIndicator, Image,
+  View, Text, ScrollView, ActivityIndicator,
 } from 'react-native';
 import { Ionicons } from '@expo/vector-icons';
 import { router, useLocalSearchParams } from 'expo-router';
@@ -99,21 +99,17 @@ export default function PostDetailScreen() {
         </View>
       ) : (
         <ScrollView>
+          {/* `compact` tells PostCard to drop the 5-line body cap and
+              render the attachment at its natural aspect ratio instead
+              of the portrait-cropped timeline preview. */}
           <PostCard
+            compact
             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={{
@@ -204,41 +200,7 @@ function DetailRow({ label, value, mono }: { label: string; value: string; mono?
   );
 }
 
-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;