feat(oxibadge): add settings screen for shifts, rounding and language

Add a settings screen (gear button on the month-confirmation screen)
to configure the expected shift times, the rounding step, the
interface language, and the time clock address — replacing the old
onboarding-only connection flow. Settings persist to the same
preferences.toml as the reader address, under a single load_settings/
save_settings command pair.

The review screen's "fix shifts" action now redistributes stacked
punches by nearest configured shift time instead of blind position,
and a stacked cell manually cleared down to one entry no longer
leaves a dangling empty input.

Assisted-by: Claude Sonnet 5 <noreply@anthropic.com>

oxibadge/src/lib/components/review/TopBar.svelte

@@ -2,7 +2,7 @@
   import { _, locale } from 'svelte-i18n';
   import { monthName } from '$lib/month';
   import { dayWord, shortSummary } from './analysis';
-  import IconButton from './IconButton.svelte';
+  import IconButton from '../IconButton.svelte';
 
   let {
     year,