feat(gui): add GUI (Test) implementation with documentation and admin support

- Add GUI (Test) module with Fyne-based interface (internal/gui/gui.go, internal/gui/server.go)
- Add CLI monitoring capability (internal/cli/monitor.go)
- Add main_cli.go entry point for CLI-only builds
- Add comprehensive documentation suite covering setup, build, quick start, and changelog
- Add admin manifest (admin.manifest) for Windows UAC elevation support
- Add rsrc.syso.json configuration for resource embedding
- Update .gitignore to exclude build scripts (*.bat, *.sh)
- Update main.go and cli.go to support dual GUI (Test)/CLI modes
- Update README.md with new project information
- Enables users to build and run both GUI (Test)and CLI versions with proper admin privileges on Windows

admin.manifest

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+  <assemblyIdentity
+    version="1.0.0.0"
+    processorArchitecture="*"
+    name="VPN.Client.CLI"
+    type="win32"
+  />
+  <description>VPN Client CLI</description>
+  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
+    <security>
+      <requestedPrivileges>
+        <requestedExecutionLevel level="requireAdministrator" uiAccess="false"/>
+      </requestedPrivileges>
+    </security>
+  </trustInfo>
+</assembly>