fix: prevent Notion OAuth popup blocking

[Pandakingxbc]

Summary

• open the OAuth popup synchronously from the user's click, then navigate it after the authorization URL is ready
• show a localized error when the browser blocks the popup
• prevent duplicate authorization requests while OAuth startup is in progress
• validate the OAuth callback message origin and close the blank popup on startup failure

Root cause

The connector UI awaited OAuth metadata discovery and dynamic client registration before calling window.open(). That delay detached popup creation from the original user gesture, so browsers could block the Notion authorization window. Repeated clicks could also create multiple pending OAuth states.

User impact

Notion one-click authorization now opens reliably. If popups are disabled, users receive an actionable message instead of seeing an apparently unresponsive button.

Validation

• npm run lint — passed; only pre-existing React Hook warnings
• npx tsc --noEmit — passed
• uv run pytest tests/unit/i18n -q — 37 passed on the v0.9.9 baseline
• production dashboard build completed successfully

[Pandakingxbc]

修复notion授权弹窗被浏览器拦截