feat(mobile): Implement Keycloak WebView authentication with HTTP callback

- Replace flutter_appauth with custom WebView implementation to resolve deep link issues
- Add KeycloakWebViewAuthService with integrated WebView for seamless authentication
- Configure Android manifest for HTTP cleartext traffic support
- Add network security config for development environment (192.168.1.11)
- Update Keycloak client to use HTTP callback endpoint (http://192.168.1.11:8080/auth/callback)
- Remove obsolete keycloak_auth_service.dart and temporary scripts
- Clean up dependencies and regenerate injection configuration
- Tested successfully on multiple Android devices (Xiaomi 2201116TG, SM A725F)

BREAKING CHANGE: Authentication flow now uses WebView instead of external browser
- Users will see Keycloak login page within the app instead of browser redirect
- Resolves ERR_CLEARTEXT_NOT_PERMITTED and deep link state management issues
- Maintains full OIDC compliance with PKCE flow and secure token storage

Technical improvements:
- WebView with custom navigation delegate for callback handling
- Automatic token extraction and user info parsing from JWT
- Proper error handling and user feedback
- Consistent authentication state management across app lifecycle

keycloak_test_app/windows/runner/main.cpp

@@ -0,0 +1,43 @@
+#include <flutter/dart_project.h>
+#include <flutter/flutter_view_controller.h>
+#include <windows.h>
+
+#include "flutter_window.h"
+#include "utils.h"
+
+int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
+                      _In_ wchar_t *command_line, _In_ int show_command) {
+  // Attach to console when present (e.g., 'flutter run') or create a
+  // new console when running with a debugger.
+  if (!::AttachConsole(ATTACH_PARENT_PROCESS) && ::IsDebuggerPresent()) {
+    CreateAndAttachConsole();
+  }
+
+  // Initialize COM, so that it is available for use in the library and/or
+  // plugins.
+  ::CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED);
+
+  flutter::DartProject project(L"data");
+
+  std::vector<std::string> command_line_arguments =
+      GetCommandLineArguments();
+
+  project.set_dart_entrypoint_arguments(std::move(command_line_arguments));
+
+  FlutterWindow window(project);
+  Win32Window::Point origin(10, 10);
+  Win32Window::Size size(1280, 720);
+  if (!window.Create(L"keycloak_test_app", origin, size)) {
+    return EXIT_FAILURE;
+  }
+  window.SetQuitOnClose(true);
+
+  ::MSG msg;
+  while (::GetMessage(&msg, nullptr, 0, 0)) {
+    ::TranslateMessage(&msg);
+    ::DispatchMessage(&msg);
+  }
+
+  ::CoUninitialize();
+  return EXIT_SUCCESS;
+}