[client] UI refactor (#6069)

Refactor UI

---------

Co-authored-by: Eduard Gert <kontakt@eduardgert.de>
Co-authored-by: braginini <bangvalo@gmail.com>
Co-authored-by: Pascal Fischer <32096965+pascal-fischer@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: riccardom <riccardomanfrin@gmail.com>

client/ui/grpc.go

@@ -0,0 +1,67 @@
+//go:build !android && !ios && !freebsd && !js
+
+package main
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+	"sync"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/backoff"
+	"google.golang.org/grpc/credentials/insecure"
+
+	"github.com/netbirdio/netbird/client/proto"
+	"github.com/netbirdio/netbird/client/ui/desktop"
+)
+
+// Conn is the lazy, lock-protected gRPC connection shared by all services so they reuse one channel.
+type Conn struct {
+	addr string
+
+	mu     sync.Mutex
+	client proto.DaemonServiceClient
+}
+
+func NewConn(addr string) *Conn {
+	return &Conn{addr: addr}
+}
+
+func (c *Conn) Client() (proto.DaemonServiceClient, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.client != nil {
+		return c.client, nil
+	}
+
+	cc, err := grpc.NewClient(
+		strings.TrimPrefix(c.addr, "tcp://"),
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+		grpc.WithUserAgent(desktop.GetUIUserAgent()),
+		// Cap reconnect backoff at 5s; gRPC's default 120s MaxDelay would
+		// leave the UI waiting 30-60s to notice a freshly-started daemon.
+		grpc.WithConnectParams(grpc.ConnectParams{
+			Backoff: backoff.Config{
+				BaseDelay:  1 * time.Second,
+				Multiplier: 1.6,
+				Jitter:     0.2,
+				MaxDelay:   5 * time.Second,
+			},
+		}),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("dial daemon: %w", err)
+	}
+	c.client = proto.NewDaemonServiceClient(cc)
+	return c.client, nil
+}
+
+// DaemonAddr returns the default daemon gRPC address: a Unix socket on Linux/macOS, TCP loopback on Windows.
+func DaemonAddr() string {
+	if runtime.GOOS == "windows" {
+		return "tcp://127.0.0.1:41731"
+	}
+	return "unix:///var/run/netbird.sock"
+}