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/wallet/WalletDetailPane.tsx

@@ -0,0 +1,147 @@
+// WalletDetailPane — right pane of the Wallet section. Either the
+// selected tx's detail or a placeholder when nothing is selected.
+
+import React, { useEffect, useState } from 'react';
+import { useStore } from '@/lib/store';
+import { getTxDetail, type TxDetail } from '@/lib/api';
+import { shortAddr } from '@/lib/crypto';
+
+function formatT(ut: number | string): string {
+  const n = typeof ut === 'string' ? parseInt(ut, 10) : ut;
+  if (!Number.isFinite(n)) return '—';
+  return (n / 1_000_000).toLocaleString(undefined, { maximumFractionDigits: 6 });
+}
+
+export function WalletDetailPane(): React.ReactElement {
+  const sel = useStore(s => s.walletSel);
+  const keyFile = useStore(s => s.keyFile);
+  const [tx, setTx]   = useState<TxDetail | null>(null);
+  const [loading, setLoading] = useState(false);
+
+  useEffect(() => {
+    if (sel.kind !== 'tx') { setTx(null); return; }
+    let cancelled = false;
+    setLoading(true);
+    getTxDetail(sel.id)
+      .then(t => { if (!cancelled) setTx(t); })
+      .catch(() => { if (!cancelled) setTx(null); })
+      .finally(() => { if (!cancelled) setLoading(false); });
+    return () => { cancelled = true; };
+  }, [sel]);
+
+  if (sel.kind !== 'tx') {
+    return (
+      <div style={{
+        height: '100%', display: 'flex',
+        alignItems: 'center', justifyContent: 'center',
+        color: '#6a6a6a', fontSize: 13, padding: 40, textAlign: 'center',
+      }}>
+        Pick a transaction from the list on the left to see its details.
+      </div>
+    );
+  }
+
+  if (loading) return <Placeholder note="Loading…" />;
+  if (!tx)     return <Placeholder note="Transaction not found on this node." />;
+
+  const outgoing = !!keyFile && tx.from === keyFile.pub_key;
+  const amountUT = tx.amount_ut;
+  const amountColor = amountUT === 0 ? '#8b8b8b'
+    : outgoing ? '#f0b35a' : '#3ba55d';
+
+  return (
+    <div style={{
+      height: '100%', overflowY: 'auto',
+      padding: '20px 24px', background: '#000',
+    }}>
+      <div style={{ color: '#8b8b8b', fontSize: 11, letterSpacing: 1, textTransform: 'uppercase' }}>
+        {tx.type.replace(/_/g, ' ')}
+      </div>
+      <div style={{
+        color: amountColor, fontSize: 30, fontWeight: 800, marginTop: 4,
+      }}>
+        {amountUT === 0 ? '—' : `${outgoing ? '−' : '+'}${formatT(amountUT)} T`}
+      </div>
+      {tx.memo && (
+        <div style={{ color: '#e0e0e0', fontSize: 13, marginTop: 6, fontStyle: 'italic' }}>
+          “{tx.memo}”
+        </div>
+      )}
+
+      <div style={{
+        marginTop: 22, display: 'grid',
+        gridTemplateColumns: 'minmax(120px, auto) 1fr', rowGap: 10, columnGap: 20,
+      }}>
+        <Cell label="ID">{tx.id}</Cell>
+        <Cell label="From">{tx.from_addr ?? shortAddr(tx.from, 8)}</Cell>
+        {tx.to && <Cell label="To">{tx.to_addr ?? shortAddr(tx.to, 8)}</Cell>}
+        <Cell label="Amount">{formatT(tx.amount_ut)} T</Cell>
+        <Cell label="Fee">{formatT(tx.fee_ut)} T</Cell>
+        <Cell label="Time">{new Date(tx.time).toLocaleString()}</Cell>
+        <Cell label="Block">#{tx.block_index} · {shortAddr(tx.block_hash, 8)}</Cell>
+        {typeof tx.gas_used === 'number' && tx.gas_used > 0 && (
+          <Cell label="Gas used">{tx.gas_used.toLocaleString()}</Cell>
+        )}
+      </div>
+
+      {Boolean(tx.payload) && (
+        <details style={{
+          marginTop: 22, background: '#0a0a0a',
+          borderRadius: 10, border: '1px solid #1f1f1f', padding: 12,
+        }}>
+          <summary style={{ cursor: 'pointer', color: '#8b8b8b', fontSize: 12, fontWeight: 700 }}>
+            Payload
+          </summary>
+          <pre className="selectable" style={{
+            marginTop: 8, color: '#d0d0d0', fontSize: 11, lineHeight: 1.5,
+            whiteSpace: 'pre-wrap', wordBreak: 'break-word',
+          }}>
+{JSON.stringify(tx.payload, null, 2)}
+          </pre>
+        </details>
+      )}
+
+      {tx.payload_hex && (
+        <details style={{
+          marginTop: 10, background: '#0a0a0a',
+          borderRadius: 10, border: '1px solid #1f1f1f', padding: 12,
+        }}>
+          <summary style={{ cursor: 'pointer', color: '#8b8b8b', fontSize: 12, fontWeight: 700 }}>
+            Payload (hex)
+          </summary>
+          <div className="selectable" style={{
+            marginTop: 8, color: '#d0d0d0', fontSize: 11, fontFamily: 'monospace',
+            wordBreak: 'break-all',
+          }}>
+            {tx.payload_hex}
+          </div>
+        </details>
+      )}
+    </div>
+  );
+}
+
+function Cell({ label, children }: { label: string; children: React.ReactNode }) {
+  return (
+    <>
+      <div style={{
+        color: '#8b8b8b', fontSize: 11, fontWeight: 700,
+        letterSpacing: 1, textTransform: 'uppercase',
+      }}>{label}</div>
+      <div className="selectable" style={{
+        color: '#fff', fontSize: 13, fontFamily: 'monospace',
+        wordBreak: 'break-all',
+      }}>{children}</div>
+    </>
+  );
+}
+
+function Placeholder({ note }: { note: string }) {
+  return (
+    <div style={{
+      height: '100%', display: 'flex',
+      alignItems: 'center', justifyContent: 'center',
+      color: '#6a6a6a', fontSize: 13, padding: 40,
+    }}>{note}</div>
+  );
+}