[Android/iOS build] Missing context menu on Android/iOS and native text-selection toolbar

**Problem**

`dioxus-desktop` defaults` disable_context_menu = !cfg!(debug_assertions)` (config.rs:117), injecting a global contextmenu → `preventDefault()` script in release builds only.
On Android/iOS, this also suppresses the native `FloatingActionMode `(cut/copy/paste/select-all toolbar) triggered by WebView text selection. Result: no copy/paste toolbar in any Dioxus mobile release APK/IPA.

**Steps To Reproduce**

Steps to reproduce the behavior:

- Create any Dioxus mobile app with a text input
- Build a release APK: dx bundle --platform android --release
- Install and long-press a text input on the device
- The cut/copy/paste/select-all floating toolbar never appears

**Expected behavior**

The native text-selection toolbar (cut/copy/paste/select-all) should appear on long-press in release builds, same as in debug.

**Screenshots**

**Environment:**

- Dioxus version: 0.7.9
- Rust version: 1.91.1
- OS info: Android 15 (API 35)
- App platform: mobile (Android)

**Questionnaire**

I would like to fix and I have a solution.

**Proposed fix**

`disable_context_menu` is a desktop-only concept and should not be inherited by dioxus-mobile's Config default.
The fix is to override it to false in mobile's default config, keeping desktop behavior unchanged:

// dioxus-mobile Config::new() / Default impl
disable_context_menu: false,

Commencez par config.rs:117 de dioxus-desktop ainsi que par Config::new() ou l’implémentation de Default de dioxus-mobile. Créez une release mobile avec `dx bundle --platform android --release`, vérifiez qu’un appui prolongé sur un champ de saisie de texte affiche la barre d’outils native couper/copier/coller, et confirmez que le comportement du menu contextuel sur desktop reste inchangé.

Rédigé par le modèle d'indexation à partir du texte de l'issue.