Add cxyz Android project structure and initial configuration

- Introduced a new Flutter project for the cxyz Android manga/comic reader, including essential files such as pubspec.yaml, AndroidManifest.xml, and Gradle configuration.
- Added .gitignore files to exclude unnecessary files and directories for both the main project and Android-specific files.
- Implemented initial README.md with project description, features, setup instructions, and API details for ComicLand, MangaRead, and MangaTown.
- Configured analysis options and dependencies in pubspec.yaml to support Flutter development.
- Established a pnpm workspace and lockfile for dependency management.
- Included various Android resources such as icons, styles, and launch backgrounds for a complete application setup.

cxyz-android/lib/sources/source_flags.dart

@@ -0,0 +1,37 @@
+import 'source.dart';
+
+/// Compile-time source gate: `--dart-define=SOURCES=comicland,mangaread,mangatown`
+/// or `--dart-define=SOURCES=all`.
+///
+/// Unset / invalid → ComicLand only. Default is **not** all sources.
+const String kSourcesDefine = String.fromEnvironment(
+  'SOURCES',
+  defaultValue: 'comicland',
+);
+
+/// Parses [raw] into enabled [SourceId]s.
+///
+/// - Token `all` (case-insensitive) enables every [SourceId].
+/// - Unknown tokens ignored.
+/// - Empty result falls back to `{SourceId.comicland}`.
+Set<SourceId> parseEnabledSourceIds([String raw = kSourcesDefine]) {
+  final parts = raw.split(',').map((p) => p.trim().toLowerCase()).where(
+        (p) => p.isNotEmpty,
+      );
+  for (final part in parts) {
+    if (part == 'all') {
+      return SourceId.values.toSet();
+    }
+  }
+  final out = <SourceId>{};
+  for (final part in parts) {
+    final id = SourceId.tryParse(part);
+    if (id != null) out.add(id);
+  }
+  if (out.isEmpty) {
+    return {SourceId.comicland};
+  }
+  return out;
+}
+
+Set<SourceId> enabledSourceIds() => parseEnabledSourceIds();