feat(desktop): Feed + Wallet sections (v2.2.0-alpha6)

Desktop client reaches full feature parity with mobile for the two
heaviest sections. Contacts + Devices screen + polish pass remain for
rc1.

Feed section (src/sections/feed/ + src/lib/feed.ts):
  * Left pane — FeedTabs: For You / Following / Trending 24h + a
    hashtag input that promotes to a tab on Enter; breadcrumb back-
    navigation when you drill into an author wall or hashtag.
  * Right pane — FeedPane: two sub-columns. Scrollable post list
    (truncated body, likes/views/hashtags footer, active highlight)
    + PostDetail with full body, hashtag links (click → hashtag tab),
    inline attachment image, like/unlike button, Delete (if mine).
    On-mount side-effects: bumpView + fetchStats for liked-by-me.
  * ComposeModal — new-post dialog. Ctrl/Cmd+N opens it; Ctrl+Enter
    submits. Byte counter against 4000 limit, live hashtag preview.
    Uses publishAndCommit (server-side image scrub happens when
    attachments land in rc1).
  * lib/feed.ts — full mirror of mobile's feed.ts:
    fetchForYou/Timeline/Trending/Author/Hashtag/Post/Stats,
    bumpView, like/unlike/delete/follow/unfollow, publishPost +
    publishAndCommit + buildCreatePostTx. Uses window.crypto.subtle
    for SHA-256 (no expo-crypto dep). Same canonical-bytes as mobile.

Wallet section (src/sections/wallet/ + new bits in src/lib/api.ts):
  * WalletOverview (left): account card (balance + shortened pub +
    Send/Receive/Refresh) and transaction history grouped by row.
    Amount colour-codes by direction; pretty tx-type labels.
  * WalletDetailPane (right): selected tx — big signed amount,
    2-column key/value grid (id, from, to, amount, fee, time, block,
    gas), collapsible JSON payload + payload_hex fallback. Mirror of
    mobile /tx/[id] layout.
  * SendModal — transfer tx with @username / DC-address / hex pub
    resolution via resolveAccount. Balance + fee preview; refuses
    self-transfer (would roundtrip through mempool for no reason).
  * ReceiveModal — pub + Copy button. QR in rc1 once we pull in a
    qrcode lib.
  * lib/api.ts: TxRow + TxDetail types, getTxHistory, getTxDetail,
    resolveAccount (handles hex/@username/DC-address).

Store adds feedTab + feedSelectedPost + walletSel so selection state
survives section-switches. FeedTab discriminated union covers the
hashtag + author sub-states so breadcrumbs know what to render.

Typecheck + renderer build both pass. Node API used as-is — no
server changes in this release.

desktop/src/sections/feed/PostList.tsx

@@ -0,0 +1,93 @@
+// PostList — rows within the Feed middle column. Clicking a row sets
+// the selected post in the store; the detail pane reacts.
+
+import React from 'react';
+import { useStore } from '@/lib/store';
+import type { FeedPostItem } from '@/lib/feed';
+import { shortAddr } from '@/lib/crypto';
+
+interface Props {
+  posts:    FeedPostItem[];
+  activeID: string | null;
+}
+
+export function PostList({ posts, activeID }: Props): React.ReactElement {
+  const select = useStore(s => s.setFeedSelectedPost);
+  return (
+    <div>
+      {posts.map(p => (
+        <PostRow
+          key={p.post_id}
+          post={p}
+          active={p.post_id === activeID}
+          onClick={() => select(p.post_id)}
+        />
+      ))}
+    </div>
+  );
+}
+
+function PostRow({ post, active, onClick }: {
+  post: FeedPostItem; active: boolean; onClick: () => void;
+}) {
+  const author = shortAddr(post.author, 6);
+  return (
+    <div
+      onClick={onClick}
+      style={{
+        padding: '12px 14px', borderBottom: '1px solid #1f1f1f',
+        cursor: 'pointer',
+        background: active ? '#0a1a29' : 'transparent',
+      }}
+      onMouseEnter={e => { if (!active) (e.currentTarget as HTMLDivElement).style.background = '#0a0a0a'; }}
+      onMouseLeave={e => { if (!active) (e.currentTarget as HTMLDivElement).style.background = 'transparent'; }}
+    >
+      <div style={{
+        display: 'flex', alignItems: 'center', gap: 8,
+        color: '#8b8b8b', fontSize: 11, marginBottom: 4,
+      }}>
+        <span style={{ fontFamily: 'monospace', color: '#d0d0d0' }}>{author}</span>
+        <span>·</span>
+        <span>{formatRelative(post.created_at)}</span>
+      </div>
+      <div className="selectable" style={{
+        color: '#fff', fontSize: 13, lineHeight: 1.45,
+        whiteSpace: 'pre-wrap', wordBreak: 'break-word',
+        // Visual truncate; the detail pane shows the full thing.
+        display: '-webkit-box',
+        WebkitLineClamp: 4,
+        WebkitBoxOrient: 'vertical',
+        overflow: 'hidden',
+      } as React.CSSProperties}>
+        {post.content}
+      </div>
+      {post.has_attachment && (
+        <div style={{ color: '#6a6a6a', fontSize: 11, marginTop: 4 }}>
+          🖼 attachment
+        </div>
+      )}
+      <div style={{
+        color: '#6a6a6a', fontSize: 11, marginTop: 6,
+        display: 'flex', gap: 12,
+      }}>
+        <span>❤ {post.likes}</span>
+        <span>👁 {post.views}</span>
+        {post.hashtags && post.hashtags.length > 0 && (
+          <span style={{ color: '#1d9bf0' }}>
+            {post.hashtags.slice(0, 3).map(t => `#${t}`).join(' ')}
+          </span>
+        )}
+      </div>
+    </div>
+  );
+}
+
+function formatRelative(unixSec: number): string {
+  const diff = Math.floor(Date.now() / 1000) - unixSec;
+  if (diff < 60)    return `${diff}s`;
+  if (diff < 3600)  return `${Math.floor(diff / 60)}m`;
+  if (diff < 86400) return `${Math.floor(diff / 3600)}h`;
+  if (diff < 604800) return `${Math.floor(diff / 86400)}d`;
+  const d = new Date(unixSec * 1000);
+  return d.toLocaleDateString([], { month: 'short', day: 'numeric' });
+}