Add app source and tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/build_service_test.dart

@@ -0,0 +1,49 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:peach/Peach/about/internal/application/ServiceConfig.dart';
+import 'package:peach/Peach/about/internal/file/BuildService.dart';
+
+void main() {
+  test('runs custom build command and picks the runnable jar', () async {
+    // Fake Gradle project with several jars in build/libs.
+    final dir = Directory.systemTemp.createTempSync('peachdeploy_build_test');
+    addTearDown(() => dir.deleteSync(recursive: true));
+
+    File('${dir.path}/build.gradle').writeAsStringSync('// fake');
+    final libs = Directory('${dir.path}/build/libs')..createSync(recursive: true);
+    // Distractors that must be excluded, plus the real artifact.
+    File('${libs.path}/app-sources.jar').writeAsStringSync('x');
+    File('${libs.path}/app-plain.jar').writeAsStringSync('x');
+    File('${libs.path}/app.jar').writeAsStringSync('runnable');
+
+    final svc = ServiceConfig(
+      name: 'demo',
+      localProjectPath: dir.path,
+      // Trivial command so we don't need a real Gradle install.
+      buildCommand: Platform.isWindows ? 'echo building' : 'true',
+    );
+
+    final build = BuildService();
+    addTearDown(build.dispose);
+
+    final result = await build.build(svc);
+
+    expect(result.ok, isTrue, reason: result.message);
+    expect(result.jar, isNotNull);
+    expect(result.jar!.path.replaceAll('\\', '/'), endsWith('app.jar'));
+  });
+
+  test('reports a helpful error when no project is detected', () async {
+    final dir = Directory.systemTemp.createTempSync('peachdeploy_empty_test');
+    addTearDown(() => dir.deleteSync(recursive: true));
+
+    final svc = ServiceConfig(name: 'empty', localProjectPath: dir.path);
+    final build = BuildService();
+    addTearDown(build.dispose);
+
+    final result = await build.build(svc);
+    expect(result.ok, isFalse);
+    expect(result.message.toLowerCase(), contains('detect'));
+  });
+}