Add WireGuard TUI implementation

- Add Go TUI with bubbletea for WireGuard management
- Implement client CRUD operations with QR code generation
- Add configuration and validation modules
- Install/update scripts for client setup
- Update Makefile to build binaries to bin/ directory
- Add .gitignore for Go projects

internal/tui/theme/theme.go

@@ -0,0 +1,185 @@
+package theme
+
+import (
+	"fmt"
+	"os"
+	"sync"
+
+	"github.com/charmbracelet/lipgloss"
+)
+
+// ColorScheme defines the color palette for the theme
+type ColorScheme struct {
+	Primary    lipgloss.Color
+	Success    lipgloss.Color
+	Warning    lipgloss.Color
+	Error      lipgloss.Color
+	Muted      lipgloss.Color
+	Background lipgloss.Color
+}
+
+// Theme represents a color theme with its name and color scheme
+type Theme struct {
+	Name   string
+	Scheme ColorScheme
+}
+
+// Global variables for current theme and styles
+var (
+	currentTheme *Theme
+	once         sync.Once
+
+	// Global styles that can be used throughout the application
+	StylePrimary  lipgloss.Style
+	StyleSuccess  lipgloss.Style
+	StyleWarning  lipgloss.Style
+	StyleError    lipgloss.Style
+	StyleMuted    lipgloss.Style
+	StyleTitle    lipgloss.Style
+	StyleSubtitle lipgloss.Style
+	StyleHelpKey  lipgloss.Style
+)
+
+// DefaultTheme is the standard blue-based theme
+var DefaultTheme = &Theme{
+	Name: "default",
+	Scheme: ColorScheme{
+		Primary:    lipgloss.Color("62"),  // Blue
+		Success:    lipgloss.Color("46"),  // Green
+		Warning:    lipgloss.Color("208"), // Orange
+		Error:      lipgloss.Color("196"), // Red
+		Muted:      lipgloss.Color("241"), // Gray
+		Background: lipgloss.Color(""),    // Default terminal background
+	},
+}
+
+// DarkTheme is a purple-based dark theme
+var DarkTheme = &Theme{
+	Name: "dark",
+	Scheme: ColorScheme{
+		Primary:    lipgloss.Color("141"), // Purple
+		Success:    lipgloss.Color("51"),  // Cyan
+		Warning:    lipgloss.Color("226"), // Yellow
+		Error:      lipgloss.Color("196"), // Red
+		Muted:      lipgloss.Color("245"), // Light gray
+		Background: lipgloss.Color(""),    // Default terminal background
+	},
+}
+
+// LightTheme is a green-based light theme
+var LightTheme = &Theme{
+	Name: "light",
+	Scheme: ColorScheme{
+		Primary:    lipgloss.Color("34"),  // Green
+		Success:    lipgloss.Color("36"),  // Teal
+		Warning:    lipgloss.Color("214"), // Amber
+		Error:      lipgloss.Color("196"), // Red
+		Muted:      lipgloss.Color("244"), // Gray
+		Background: lipgloss.Color(""),    // Default terminal background
+	},
+}
+
+// ThemeRegistry holds all available themes
+var ThemeRegistry = map[string]*Theme{
+	"default": DefaultTheme,
+	"dark":    DarkTheme,
+	"light":   LightTheme,
+}
+
+// GetTheme loads the theme from config or environment variable
+// Returns the default theme if no theme is specified
+func GetTheme() (*Theme, error) {
+	once.Do(func() {
+		// Try to get theme from environment variable first
+		themeName := os.Getenv("THEME")
+		if themeName == "" {
+			themeName = "default"
+		}
+
+		// Look up the theme in the registry
+		if theme, ok := ThemeRegistry[themeName]; ok {
+			currentTheme = theme
+		} else {
+			// If theme not found, use default
+			currentTheme = DefaultTheme
+		}
+
+		// Apply the theme to initialize styles
+		ApplyTheme(currentTheme)
+	})
+
+	return currentTheme, nil
+}
+
+// ApplyTheme applies the given theme to all global styles
+func ApplyTheme(theme *Theme) {
+	currentTheme = theme
+
+	// Primary style
+	StylePrimary = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Primary)
+
+	// Success style
+	StyleSuccess = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Success)
+
+	// Warning style
+	StyleWarning = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Warning)
+
+	// Error style
+	StyleError = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Error)
+
+	// Muted style
+	StyleMuted = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Muted)
+
+	// Title style (bold primary)
+	StyleTitle = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Primary).
+		Bold(true)
+
+	// Subtitle style (muted)
+	StyleSubtitle = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Muted)
+
+	// Help key style (bold primary, slightly different shade)
+	StyleHelpKey = lipgloss.NewStyle().
+		Foreground(theme.Scheme.Primary).
+		Bold(true)
+}
+
+// GetThemeNames returns a list of available theme names
+func GetThemeNames() []string {
+	names := make([]string, 0, len(ThemeRegistry))
+	for name := range ThemeRegistry {
+		names = append(names, name)
+	}
+	return names
+}
+
+// SetTheme changes the current theme by name
+func SetTheme(name string) error {
+	theme, ok := ThemeRegistry[name]
+	if !ok {
+		return fmt.Errorf("theme '%s' not found. Available themes: %v", name, GetThemeNames())
+	}
+
+	ApplyTheme(theme)
+	return nil
+}
+
+// GetCurrentTheme returns the currently active theme
+func GetCurrentTheme() *Theme {
+	if currentTheme == nil {
+		currentTheme = DefaultTheme
+		ApplyTheme(currentTheme)
+	}
+	return currentTheme
+}
+
+// GetColorScheme returns the color scheme of the current theme
+func GetColorScheme() ColorScheme {
+	return GetCurrentTheme().Scheme
+}