Android: `font`, `contentInsets`, `lineNumbers` props

[LeslieOA]

Next slice of #32. Wire the three style/layout props that are currently no-ops on the Android ViewManager.

Scope

• `font` — `{ family?: string; size?: number }`. Map to Sora's `editor.typefaceText` + `editor.textSizePx`. Default to system monospace at 14pt to match iOS/macOS `monospacedSystemFont`.
• `contentInsets` — `{ top?, bottom?, left?, right? }`. Map to the editor's padding (Sora exposes `paddingTop/Bottom/Left/Right` via standard Android `View.setPadding`). Mirror the iOS `UIEdgeInsets` semantics — applied to the text container, not the editor view's frame.
• `lineNumbers` — boolean. Sora's `CodeEditor` ships line numbers ON by default; `editor.isLineNumberEnabled = value` flips the gutter at runtime.

Replace the three no-op stubs in `SourceEditorViewManager.kt`. Forward through `SourceEditorView` setters so the prop diff path stays consistent with the existing `text` / `editable` / `language` pattern.

Update `example/expo-app/App.android.tsx` toolbar to mirror the iOS controls now that the props are real:

• LineNumbers toggle (Pressable button with `#` label, similar to iOS Toggle)
• Font/contentInsets stay as defaults — iOS doesn't expose toolbar UI for them either.

Refs #32.