feat(desktop): Electron scaffold, shell, auth + section stubs (v2.2.0-alpha4)

PR #4 of the multi-device roadmap — desktop client groundwork. The shell
compiles and runs end-to-end on top of a v2.2.0 node; sections are
placeholders that later alphas fill in with real chat / feed / wallet /
contacts / settings content shared with the mobile client-app.

Scaffold:
  * Vite + React + TypeScript renderer; Electron main/preload TS
    compiled via a separate tsconfig.
  * npm scripts — `dev` (concurrent Vite + Electron), `build`
    (installer via electron-builder), `typecheck`.
  * electron-builder targets: .dmg / .exe / .AppImage + .deb.
  * CSP pins script-src 'self'; connect-src left open so the renderer
    can hit any configured node.

Electron main + preload:
  * Frame-less window, hiddenInset on macOS, custom-overlay on Windows,
    drag region via CSS -webkit-app-region: drag on our TitleBar.
  * contextIsolation on, nodeIntegration off, sandbox off (needed for
    safeStorage in preload).
  * window.dchain.keyfile.{load,save,delete,encryptionAvailable} —
    keyfile lives in the OS keychain via Electron safeStorage, with a
    plaintext fallback for OSes without an encryption backend.
  * window.dchain.dialog.{openFile,saveFile}, .fs.{readText,writeText},
    .app.{version,platform}. Everything else still goes over plain
    fetch() in the renderer.

Shell (src/shell/):
  * TitleBar — draggable 32px strip; DChain brand.
  * NavBar — left 72px rail, six sections + Cmd+1..5 keybinds.
  * StatusBar — ● online/connecting/offline dot, node URL, current
    chain height (polls /api/netstats every 5s).
  * Shell — composes the 3 panes; picks { List, Detail } by active
    section.

Sections (all stubs — filling in alpha5+):
  * Messages, Feed, Contacts, Profile — SectionPlaceholder with notes.
  * Wallet — shows the balance reading from /api/address/{pub} as a
    first real data binding.
  * Settings — node-URL card with live ping + commit, identity card
    (shows pub key), about card (reads Electron app.version via IPC).

Auth (src/auth/Welcome.tsx):
  * Create — generates Ed25519 + X25519 via tweetnacl, saves via IPC.
  * Import — Electron dialog.openFile → parses node.json → saves.
  * Pair — stub routed; real poll loop reuses the mobile flow in
    alpha5.

Lib (src/lib/):
  * types.ts — KeyFile / Contact / Message / NodeSettings mirroring
    client-app wire formats.
  * storage.ts — keyfile via IPC, settings + contacts + device-registered
    marker via localStorage.
  * api.ts — fetch wrapper with setNodeUrl + onNodeUrlChange;
    getNetStats, getIdentity, fetchDevices, getBalance bindings.
  * store.ts — zustand { booted, keyFile, settings, contacts, section }.

docs/ROADMAP.md — desktop subsection updated with per-alpha breakdown.

Next (alpha5): Messages section wired to the relay mailbox, full
conversation view, and the pairing poll loop.

docs/ROADMAP.md

@@ -186,14 +186,22 @@ desktop/
 └── package.json
 ```
 
-### План работ (отдельно, после v2.2.0-alpha3)
+### План работ
 
-- [ ] Boilerplate: Electron + Vite + React + TS, frame-less window, 3-panel shell.
-- [ ] Сопрягание `lib/` из client-app (заменить expo-* на Electron-эквиваленты).
-- [ ] Sections по порядку: Messages → Feed → Wallet → Contacts → Settings → Profile.
-- [ ] Multi-device pairing flow (использует v2.2.0 registry).
-- [ ] Auto-update через electron-updater или через тот же `/api/update-check`.
-- [ ] Packaging: `electron-builder` → `.dmg`, `.exe`, `.AppImage`, `.deb`.
+- [x] **v2.2.0-alpha4** — Boilerplate: Electron + Vite + React + TS,
+      frame-less window, 3-panel shell, nav + status bar, safeStorage
+      for keyfile via IPC, Welcome + Create/Import auth flow, section
+      stubs that the rest of the alphas will fill in.
+- [ ] **v2.2.0-alpha5** — Messages section (chat list + conversation)
+      using the same fan-out semantics as mobile. Pairing flow wired up
+      (new-device poll loop + primary-device modal reused from mobile).
+- [ ] **v2.2.0-alpha6** — Feed + Wallet real content (reuse feed.ts /
+      tx builders from client-app via a shared workspace package).
+- [ ] **v2.2.0-rc1** — Contacts + Settings → Devices + Profile,
+      polish pass (keybinds, focus, drag-drop attachments).
+- [ ] **v2.2.0** — Auto-update through the same `/api/update-check`
+      pipeline nodes use; `electron-builder` → `.dmg`, `.exe`,
+      `.AppImage`, `.deb`.
 
 ### Открытые вопросы (desktop)