[client] Start the restarted UI with the user's environment block (#7245)

The updater runs as LocalSystem and started netbird-ui via
CreateProcessAsUser with a nil environment, so the UI inherited the
SYSTEM environment (USERPROFILE, APPDATA pointing at systemprofile)
while running under the user's token. The WebView2-based UI exits
immediately in that state, so the UI never came back after an update.

Build the environment from the user's token with CreateEnvironmentBlock
and pass it to CreateProcessAsUser.

client/internal/updater/installer/installer_run_windows.go

@@ -307,6 +307,16 @@ func startUIInSession(uiPath string, sessionID uint32) error {
 		}
 	}()
 
+	var env *uint16
+	if err := windows.CreateEnvironmentBlock(&env, primaryToken, false); err != nil {
+		return fmt.Errorf("create environment block: %w", err)
+	}
+	defer func() {
+		if err := windows.DestroyEnvironmentBlock(env); err != nil {
+			log.Warnf("failed to destroy environment block: %v", err)
+		}
+	}()
+
 	// Prepare startup info
 	var si windows.StartupInfo
 	si.Cb = uint32(unsafe.Sizeof(si))
@@ -329,7 +339,7 @@ func startUIInSession(uiPath string, sessionID uint32) error {
 		nil,
 		false,
 		creationFlags,
-		nil,
+		env,
 		nil,
 		&si,
 		&pi,