build(metro): add web shims for native React Native API compatibility

Add Metro configuration to resolve native-only React Native APIs with web-compatible shims. This enables packages like react-native-pager-view to work on the web platform by providing shim implementations for codegenNativeComponent, codegenNativeCommands, and CodegenTypes that are unavailable in react-native-web.

Also simplify Android signing configuration in CI by using standard Gradle property names (MYAPP_UPLOAD_*) and remove the build.gradle patching step.

web-shims/react-native/Libraries/Utilities/codegenNativeCommands.js

@@ -0,0 +1,15 @@
+function codegenNativeCommands(options) {
+  const commands = {};
+  if (options && options.supportedCommands) {
+    options.supportedCommands.forEach((commandName) => {
+      commands[commandName] = (ref, ...args) => {
+        if (ref && ref.current && typeof ref.current[commandName] === 'function') {
+          ref.current[commandName](...args);
+        }
+      };
+    });
+  }
+  return commands;
+}
+
+module.exports = codegenNativeCommands;