chore: release 0.3.1 — iOS PWA fixes, notification improvements, docs update

- fix(pwa): iOS keyboard gap caused by WebKit viewport-fit=cover bug.
  After keyboard open/close, 100dvh permanently shrinks. Track max
  innerHeight in --app-height CSS variable as stable replacement.
- feat(pwa): auto-prompt notification permission on first login in
  standalone mode (once only, skips if denied).
- refactor: remove duplicate notification toggle from header menu
  (already in Settings).
- feat(dev): expose Vite dev server on network (host: true) for
  mobile testing via Tailscale.
- docs: update README — add Task Progress FAB, fix notification
  flow description, document OPENAI_API_KEY / VAPID_EMAIL env vars,
  clarify voice input backends, add CLI --version/--help, update
  .env.example.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vite.config.ts

@@ -49,6 +49,7 @@ export default defineConfig({
     },
   },
   server: {
+    host: true,
     proxy: {
       '/api': {
         target: 'https://localhost:3456',