feat: compact boundary divider, overlay fix, approval window, PiP, Tauri enhancements

- Add CompactBoundaryDivider component for compact_boundary system messages
- Fix readability overlay: v-if removes element entirely at 0% opacity
- Add approval page and window composable
- Add PiP window support and loading screen
- Tauri: add window management commands and capabilities
- Disable Ctrl+1..5 shortcuts in Tauri (handled by global shortcuts)

frontend/package.json

@@ -24,6 +24,7 @@
     "@tauri-apps/api": "^2.10.1",
     "@tauri-apps/plugin-clipboard-manager": "^2.3.2",
     "@tauri-apps/plugin-dialog": "^2.6.0",
+    "@tauri-apps/plugin-global-shortcut": "^2.3.1",
     "@tauri-apps/plugin-http": "^2.5.7",
     "@tauri-apps/plugin-notification": "^2.3.3",
     "@tauri-apps/plugin-store": "^2.4.2",