feat(desktop): Contacts + Settings→Devices + expanded Profile + QR + keybinds (v2.2.0-rc1)

Completes the desktop feature surface ahead of the v2.2.0 tag. Only
auto-update + packaging remain.

Settings — now two-paned (nav on the left, pages on the right):
  * NodePage — URL ping-on-commit + API token field.
  * IdentityPage — pub key / X25519 pub, Export (safe-save dialog) /
    Import (open dialog + wipe + replace) / Delete identity.
  * DevicesPage — full multi-device UI: list every active device with
    a THIS DEVICE badge; Unlink button on every other row submits
    UNLINK_DEVICE + optimistic local remove; Link new device modal
    takes {code, device key, name}, submits LINK_DEVICE, then ships
    the handshake envelope (master Ed25519 priv encrypted for the
    new X25519) — same protocol as mobile's primary-device modal.
  * AboutPage — version, platform, Gitea links.
  * store.settingsPage discriminated union keeps selection across
    section switches.

Contacts section (now real):
  * ContactsList — alphabetical, filter-as-you-type; each row shows
    avatar letter + name + short address.
  * ContactsDetail — profile card (username/alias/pub) + Open chat /
    View posts / Copy address actions + stats grid
    (Balance, Devices, Encryption, Added) + Identity card with
    DC address, username, published X25519, device_count.
  * store.selectedContact persists across navigation.

Profile section (expanded):
  * ProfileList — big avatar + pub key + contacts count.
  * ProfileDetail — balance hero, quick actions (My posts →
    feed author wall, Manage devices → Settings→Devices, Copy
    address), Identity card, inline Linked devices list with a
    THIS DEVICE badge matching the Settings page.

Receive modal — canvas QR via `qrcode` (new dep, ~5 KB gzipped),
white-on-transparent so it sits inside the same black modal chrome.

Global keybinds (useGlobalKeybinds hook mounted in Shell):
  * Ctrl/Cmd+W — close the current conversation (drops activeChat,
    keeps section). Does NOT close the window.
  * Ctrl/Cmd+K — jump to Contacts.
  * Ctrl/Cmd+, — Settings.
  Each guards against being in a text field so typing `k,` in a
  composer / search doesn't hijack.

docs/ROADMAP.md — rc1 row flipped to done; v2.2.0 narrows to
auto-update + packaging + optional attachments in Compose.

desktop/src/lib/store.ts

@@ -29,6 +29,9 @@ export type WalletSelection =
   | { kind: 'overview' }
   | { kind: 'tx'; id: string };
 
+/** Which Settings subsection is visible in the detail pane. */
+export type SettingsPage = 'node' | 'identity' | 'devices' | 'about';
+
 interface State {
   booted:      boolean;
   keyFile:     KeyFile | null;
@@ -64,6 +67,14 @@ interface State {
   /** Wallet state. */
   walletSel: WalletSelection;
   setWalletSel: (s: WalletSelection) => void;
+
+  /** Settings state. */
+  settingsPage: SettingsPage;
+  setSettingsPage: (p: SettingsPage) => void;
+
+  /** Currently-selected contact in the Contacts section. */
+  selectedContact: string | null;
+  setSelectedContact: (addr: string | null) => void;
 }
 
 export const useStore = create<State>((set) => ({
@@ -119,4 +130,10 @@ export const useStore = create<State>((set) => ({
 
   walletSel: { kind: 'overview' },
   setWalletSel: (s) => set({ walletSel: s }),
+
+  settingsPage: 'node',
+  setSettingsPage: (p) => set({ settingsPage: p }),
+
+  selectedContact: null,
+  setSelectedContact: (addr) => set({ selectedContact: addr }),
 }));