fix: report the real error when the log target cannot be opened

[l1a]

Problem

When a log target cannot be opened, the error message discards the actual reason:

cannot open log target: %!s(<nil>)

I hit this with a scheduled profile whose log pointed into a directory that did not exist. The message gave me nothing to go on, and the real cause (no such file or directory) was never printed.

Cause

In main.go, err is declared in the if statement's init:

if closer, options, err := setupTargetLogger(flags, terminal, logTarget, commandOutput); err == nil {
    ...
    return
}
// fallback to a console logger
setupConsoleLogger(flags)
clog.Errorf("cannot open log target: %s", err)

Go scopes that err to the if statement, so it is out of scope by the time clog.Errorf runs. The call therefore resolves to main()'s outer var err error (main.go:39), which is still nil at that point — hence %!s(<nil>). It compiles precisely because that outer variable exists.

Fix

Hoist the call out of the if init so the error is in scope where it is logged. Two lines, no behaviour change beyond the message.

Verification

Same command, before and after:

# before
$ resticprofile --log /nonexistent-dir/test.log -n profile show
cannot open log target: %!s(<nil>)

# after
$ resticprofile --log /nonexistent-dir/test.log -n profile show
cannot open log target: open /nonexistent-dir/test.log: no such file or directory

make build and make lint pass (0 issues on darwin, linux and windows). make test shows no new failures.

I did not add a unit test: the affected code is a closure inside main(), so covering it would require refactoring setupLogging out of main — happy to do that in this PR if you would prefer it.