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/ExportModal.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
   import { _ } from 'svelte-i18n';
-  import { ROUND_STEP } from './analysis';
+  import type { Shifts } from '$lib/shifts';
   import FixButton from './FixButton.svelte';
   import ActionButton from './ActionButton.svelte';
 
@@ -8,6 +8,7 @@
     title,
     scopeIssues,
     scopeInfos,
+    shift,
     items,
     onclose,
     onroundandexport,
@@ -16,6 +17,7 @@
     title: string;
     scopeIssues: number;
     scopeInfos: number;
+    shift: Shifts;
     items: { key: string; label: string; detail: string; red: boolean; go: () => void }[];
     onclose: () => void;
     onroundandexport: () => void;
@@ -40,7 +42,7 @@
         {#if scopeIssues}
           {$_('review.export_warning_issues')}
         {:else}
-          {$_('review.export_warning_unrounded', { values: { step: ROUND_STEP } })}
+          {$_('review.export_warning_unrounded', { values: { step: shift.round_step_min } })}
         {/if}
       </p>
     </div>