fix(restart): the self-relaunch waits for its parent's mutex

A database switch relaunches OpsLog, and the child regularly won the
race against the old instance's teardown — so following the app's own
instructions produced 'OpsLog is already running'. The relaunch now
passes --relaunch, which gets the same 20-second mutex patience the
post-update restart has always had. Opens the 0.27.6 block.

app.go

@@ -2851,7 +2851,9 @@ func (a *App) RestartApp() error {
 	if err != nil {
 		return fmt.Errorf("locate executable: %w", err)
 	}
-	cmd := exec.Command(exe)
+	// --relaunch: the child waits for OUR mutex instead of declaring us a
+	// duplicate — this instance is quitting, just not always fast enough.
+	cmd := exec.Command(exe, "--relaunch")
 	cmd.Dir = filepath.Dir(exe)
 	if err := cmd.Start(); err != nil {
 		return fmt.Errorf("relaunch OpsLog: %w", err)