Fix paste-to-app, settings highlight, and titleBarStyle casing

Paste fix:
- Switch from std::process::Command to tokio::process::Command to avoid
  blocking the async runtime (was stalling the paste action)
- Use explicit AppleScript that activates the frontmost app before sending
  Cmd+V keystroke, making paste more reliable
- Increase delay to 300ms for macOS app refocus
- Add tokio "process" feature

Settings highlight fix:
- SettingsPanel now uses local useState for immediate optimistic updates
  when clicking position/history buttons, instead of waiting for the
  parent prop round-trip
- Buttons highlight instantly on click, then sync with backend

Config fix:
- titleBarStyle must be PascalCase "Overlay" in Tauri 2 config (was
  lowercase "overlay" which caused a startup error)

Co-authored-by: Cursor <cursoragent@cursor.com>

src-tauri/tauri.conf.json

@@ -21,7 +21,7 @@
         "minWidth": 320,
         "minHeight": 300,
         "decorations": true,
-        "titleBarStyle": "overlay",
+        "titleBarStyle": "Overlay",
         "hiddenTitle": true,
         "visible": false,
         "alwaysOnTop": true,