feat: implement ADB wrapper and device management backend

Adds full ADB client, device manager, static DeviceInfo fetcher, and
live DeviceLiveStats poller. Exposes ListDevices, ConnectDevice,
DisconnectDevice, GetDeviceInfo, GetDeviceLiveStats as Wails-bound
methods with a 1s devices:changed event loop. Bundles ADB binary
infrastructure via //go:embed all:bin with runtime fallback chain.

backend-go/adb/client.go

@@ -1 +1,81 @@
 package adb
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+type Client struct {
+	path string
+}
+
+func New(adbPath string) *Client {
+	return &Client{path: adbPath}
+}
+
+// run executes an adb command and returns stdout.
+func (c *Client) run(ctx context.Context, args ...string) (string, error) {
+	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, c.path, args...)
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	if err := cmd.Run(); err != nil {
+		msg := strings.TrimSpace(stderr.String())
+		if msg == "" {
+			msg = err.Error()
+		}
+		return "", fmt.Errorf("adb %s: %s", strings.Join(args, " "), msg)
+	}
+	return strings.TrimSpace(stdout.String()), nil
+}
+
+// Devices returns raw output of `adb devices -l`.
+func (c *Client) Devices(ctx context.Context) (string, error) {
+	return c.run(ctx, "devices", "-l")
+}
+
+// Shell runs a shell command on a specific device and returns stdout.
+func (c *Client) Shell(ctx context.Context, deviceID, cmd string) (string, error) {
+	return c.run(ctx, "-s", deviceID, "shell", cmd)
+}
+
+// Connect connects to a device over TCP/IP (wireless ADB).
+func (c *Client) Connect(ctx context.Context, address string) (string, error) {
+	return c.run(ctx, "connect", address)
+}
+
+// Disconnect disconnects a device.
+func (c *Client) Disconnect(ctx context.Context, deviceID string) (string, error) {
+	return c.run(ctx, "disconnect", deviceID)
+}
+
+// Pull copies a file from the device to a local path.
+func (c *Client) Pull(ctx context.Context, deviceID, remotePath, localPath string) error {
+	_, err := c.run(ctx, "-s", deviceID, "pull", remotePath, localPath)
+	return err
+}
+
+// Push copies a local file to the device.
+func (c *Client) Push(ctx context.Context, deviceID, localPath, remotePath string) error {
+	_, err := c.run(ctx, "-s", deviceID, "push", localPath, remotePath)
+	return err
+}
+
+// StartServer starts the ADB server if not already running.
+func (c *Client) StartServer(ctx context.Context) error {
+	_, err := c.run(ctx, "start-server")
+	return err
+}
+
+// Path returns the resolved ADB binary path.
+func (c *Client) Path() string {
+	return c.path
+}