Fix blank Settings window with menu bar redirect

[mvanhorn]

The Settings scene used EmptyView() to satisfy SwiftUI's one-scene requirement. But pressing Cmd+, still opens it, leaving users with a blank window (#12).

Replaced with a small view that says "Clicky lives in your menu bar" and points users to the menu bar icon. Uses system SF Symbol and standard secondary text colors.

Single file changed, 15 lines added. No new dependencies, no behavior changes outside the Settings window.

Fixes #12

This contribution was developed with AI assistance (Claude Code).

[khaledmhirsi]

I could not push directly to this contributor branch (403 from GitHub), so I opened a fixed replacement PR here: #97.

The replacement keeps the original one-file fix, rebases it onto current main, and tightens the Settings message so users know to use the menu bar controls and that API keys are configured through the Worker setup rather than this blank Settings window.

Validated with:

• swiftc -parse leanring-buddy/*.swift
• npx --yes --package typescript tsc --noEmit --target ES2022 --module ESNext worker/src/index.ts
• git diff --check origin/main...HEAD

[mvanhorn]

Thanks @khaledmhirsi, #97 looks great. Closing this in favor of yours.