fix(mobile): remove Android input underline backgrounds

apps/mobile/app.config.ts

@@ -422,6 +422,7 @@ const config: ExpoConfig = {
     "./plugins/withIosSceneLifecycle.cjs",
     "./plugins/withAndroidCleartextTraffic.cjs",
     "./plugins/withAndroidGradleHeap.cjs",
+    "./plugins/withAndroidInputBackground.cjs",
     "./plugins/withAndroidModernPopupMenu.cjs",
     "./plugins/withAndroidModernAlertDialog.cjs",
     "./plugins/withAndroidPredictiveBackCompat.cjs",

apps/mobile/plugins/withAndroidInputBackground.cjs

@@ -0,0 +1,27 @@
+const { withAndroidStyles } = require("expo/config-plugins");
+
+module.exports = function withAndroidInputBackground(config) {
+  return withAndroidStyles(config, (config) => {
+    const appTheme = config.modResults.resources.style?.find(
+      (style) => style.$?.name === "AppTheme",
+    );
+    if (!appTheme) {
+      throw new Error("withAndroidInputBackground: AppTheme is missing from styles.xml.");
+    }
+
+    // Inputs draw their own backgrounds and borders. Remove the native underline
+    // drawable so it cannot peek out beneath rounded corners or return on focus.
+    // Set both attributes for AppCompat and framework EditText implementations.
+    appTheme.item ??= [];
+    for (const name of ["editTextBackground", "android:editTextBackground"]) {
+      const existing = appTheme.item.find((item) => item.$?.name === name);
+      if (existing) {
+        existing._ = "@null";
+      } else {
+        appTheme.item.push({ $: { name }, _: "@null" });
+      }
+    }
+
+    return config;
+  });
+};