Add Android Capacitor build system

- Install Capacitor dependencies (@capacitor/cli, @capacitor/core, @capacitor/android, @capacitor/app, @capacitor/status-bar, sharp)
- Create capacitor.config.ts with app configuration
- Update .gitignore to exclude Android build outputs and keystore files
- Generate icon-512.png from logo.svg
- Add scripts for icon generation, APK building, and keystore creation
- Initialize Capacitor Android platform
- Configure build.gradle with signing support
- Generate Android app icons in all required densities
- Add npm scripts: 'icons' and 'build:apk'

android/app/src/test/java/com/getcapacitor/myapp/ExampleUnitTest.java

@@ -0,0 +1,18 @@
+package com.getcapacitor.myapp;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+public class ExampleUnitTest {
+
+    @Test
+    public void addition_isCorrect() throws Exception {
+        assertEquals(4, 2 + 2);
+    }
+}