feat(tauri): add Tauri v2 Android app wrapper

- Wrap apps/web as Android APK via Tauri v2 WebView (zero web changes)
- Disable default compression feature to avoid brotli/alloc-no-stdlib conflict with Rust 1.96
- Add RGBA icon placeholders
- Add Android keystore to gitignore

APK output: apps/tauri/gen/android/app/build/outputs/apk/

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

apps/tauri/src/lib.rs

@@ -0,0 +1,6 @@
+#[cfg_attr(mobile, tauri::mobile_entry_point)]
+pub fn run() {
+    tauri::Builder::default()
+        .run(tauri::generate_context!())
+        .expect("error while running tauri application");
+}

apps/tauri/src/main.rs

@@ -0,0 +1,5 @@
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
+
+fn main() {
+    zeavis_edu_tauri::run()
+}