Add keyboard mode toggle and QR scanner improvements

- Add keyboard mode toggle button (⇧K) in sidebar
- Triple-Escape to quickly exit keyboard mode
- Extract QrScannerModal to shared component
- Add QR scanner for NWC wallet connection in Settings
- Update Help page with keyboard toggle documentation
- Fix keyboard navigation getting stuck on inbox
- Improve feed loading after login (loads immediately)
- DM conversation page layout improvements

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Sidebar/index.tsx

@@ -12,6 +12,7 @@ import BookmarkButton from './BookmarkButton'
 import HelpButton from './HelpButton'
 import HomeButton from './HomeButton'
 import InboxButton from './InboxButton'
+import KeyboardModeButton from './KeyboardModeButton'
 import LayoutSwitcher from './LayoutSwitcher'
 import NotificationsButton from './NotificationButton'
 import PostButton from './PostButton'
@@ -67,6 +68,7 @@ export default function PrimaryPageSidebar() {
       </div>
       <div className="space-y-4">
         <HelpButton collapse={isCollapsed} navIndex={pubkey ? 8 : 6} />
+        <KeyboardModeButton collapse={isCollapsed} />
         <LayoutSwitcher collapse={isCollapsed} />
         <AccountButton collapse={isCollapsed} />
       </div>