feat: initialize Flutter project with version management

- Initialize Flutter 3.38 project with all platforms
- Add build-time version generation from pubspec.yaml
- Print version to console on app startup
- Create CHANGELOG.md following Keep a Changelog format
- Update .gitignore for Flutter + generated files
- Basic app scaffold with Material 3 theming

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

linux/flutter/generated_plugin_registrant.h

@@ -0,0 +1,15 @@
+//
+//  Generated file. Do not edit.
+//
+
+// clang-format off
+
+#ifndef GENERATED_PLUGIN_REGISTRANT_
+#define GENERATED_PLUGIN_REGISTRANT_
+
+#include <flutter_linux/flutter_linux.h>
+
+// Registers Flutter plugins.
+void fl_register_plugins(FlPluginRegistry* registry);
+
+#endif  // GENERATED_PLUGIN_REGISTRANT_