fix(android): P3 keyboard-hint sweep + clipboard JNI verified

Suppress all remaining keyboard-accelerator chips/labels on Android:
- spawn_modal_button (ui_modal.rs): single cfg gate covers every modal
  across all 13+ callers (onboarding, pause, confirm, game-over, restore,
  play-by-seed, home, help, profile, stats, leaderboard, settings, achievement)
- home_plugin.rs: mode-card hotkey chips (N/C/Z/X/T) gated off
- replay_overlay.rs: [SPACE]/[ESC]/[←→] footer hint text gated off;
  mode-indicator text kept
- help_plugin.rs: kbd chip containers gated off; description text kept

Clipboard JNI verified on Pixel 7 AVD (Android 14): added temporary
KEYCODE_C test hook, logcat confirmed "clipboard JNI OK", hook reverted.
Both JNI bridges (keystore + clipboard) are now confirmed working on device.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/ui_modal.rs

@@ -328,6 +328,8 @@ pub fn spawn_modal_button<M: Component>(
     variant: ButtonVariant,
     font_res: Option<&FontResource>,
 ) {
+    #[cfg(target_os = "android")]
+    let hotkey = None;
     let font_handle = font_res.map(|f| f.0.clone()).unwrap_or_default();
     let font_label = TextFont {
         font: font_handle.clone(),