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/screens/qr.go

@@ -0,0 +1,141 @@
+package screens
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/calmcacil/wg-admin/internal/wireguard"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+	"github.com/mdp/qrterminal/v3"
+)
+
+// QRScreen displays a QR code for a WireGuard client configuration
+type QRScreen struct {
+	clientName    string
+	configContent string
+	qrCode        string
+	inlineMode    bool
+	width, height int
+	errorMsg      string
+}
+
+// NewQRScreen creates a new QR screen for displaying client config QR codes
+func NewQRScreen(clientName string) *QRScreen {
+	return &QRScreen{
+		clientName: clientName,
+		inlineMode: true, // Start in inline mode
+	}
+}
+
+// Init initializes the QR screen
+func (s *QRScreen) Init() tea.Cmd {
+	return s.loadConfig
+}
+
+// Update handles messages for the QR screen
+func (s *QRScreen) Update(msg tea.Msg) (Screen, tea.Cmd) {
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		switch msg.String() {
+		case "q", "escape":
+			// Return to list screen (parent should handle this)
+			return nil, nil
+		case "f":
+			// Toggle between inline and fullscreen mode
+			s.inlineMode = !s.inlineMode
+			s.generateQRCode()
+		}
+	case tea.WindowSizeMsg:
+		// Handle terminal resize
+		s.width = msg.Width
+		s.height = msg.Height
+		s.generateQRCode()
+	case configLoadedMsg:
+		s.configContent = msg.content
+		s.generateQRCode()
+	case errMsg:
+		s.errorMsg = msg.err.Error()
+	}
+
+	return s, nil
+}
+
+// View renders the QR screen
+func (s *QRScreen) View() string {
+	if s.errorMsg != "" {
+		return s.renderError()
+	}
+	if s.qrCode == "" {
+		return "Loading QR code..."
+	}
+	return s.renderQR()
+}
+
+// loadConfig loads the client configuration
+func (s *QRScreen) loadConfig() tea.Msg {
+	content, err := wireguard.GetClientConfigContent(s.clientName)
+	if err != nil {
+		return errMsg{err: err}
+	}
+	return configLoadedMsg{content: content}
+}
+
+// generateQRCode generates the QR code based on current mode and terminal size
+func (s *QRScreen) generateQRCode() {
+	if s.configContent == "" {
+		return
+	}
+
+	// Generate QR code and capture output
+	var builder strings.Builder
+
+	// Generate ANSI QR code using half-block characters
+	qrterminal.GenerateHalfBlock(s.configContent, qrterminal.L, &builder)
+
+	s.qrCode = builder.String()
+}
+
+// renderQR renders the QR code with styling
+func (s *QRScreen) renderQR() string {
+	styleTitle := lipgloss.NewStyle().
+		Foreground(lipgloss.Color("62")).
+		Bold(true).
+		MarginBottom(1)
+
+	styleHelp := lipgloss.NewStyle().
+		Foreground(lipgloss.Color("241")).
+		MarginTop(1)
+
+	styleQR := lipgloss.NewStyle().
+		MarginLeft(2)
+
+	title := styleTitle.Render(fmt.Sprintf("QR Code: %s", s.clientName))
+	help := "Press [f] to toggle fullscreen • Press [q/Escape] to return"
+
+	return title + "\n\n" + styleQR.Render(s.qrCode) + "\n" + styleHelp.Render(help)
+}
+
+// renderError renders an error message
+func (s *QRScreen) renderError() string {
+	styleError := lipgloss.NewStyle().
+		Foreground(lipgloss.Color("196")).
+		Bold(true)
+
+	styleHelp := lipgloss.NewStyle().
+		Foreground(lipgloss.Color("241")).
+		MarginTop(1)
+
+	title := styleError.Render("Error")
+	message := s.errorMsg
+	help := "Press [q/Escape] to return"
+
+	return title + "\n\n" + message + "\n" + styleHelp.Render(help)
+}
+
+// Messages
+
+// configLoadedMsg is sent when the client configuration is loaded
+type configLoadedMsg struct {
+	content string
+}