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/routes/+page.svelte

@@ -9,24 +9,41 @@
   import ConfirmMonth from '$lib/components/ConfirmMonth.svelte';
   import LoadingScreen from '$lib/components/LoadingScreen.svelte';
   import TimesheetReview from '$lib/components/TimesheetReview.svelte';
+  import SettingsButton from '$lib/components/SettingsButton.svelte';
+  import Settings from '$lib/components/Settings.svelte';
   import { buildEmployees, type AttendanceRecord } from '$lib/components/review/fromRecords';
+  import type { Shifts } from '$lib/shifts';
+  import type { Settings as SettingsData } from '$lib/settings';
 
-  type Step = 'loading' | 'setup' | 'confirm-month' | 'loading-records' | 'loading-employees' | 'review';
+  type Step = 'loading' | 'setup' | 'confirm-month' | 'loading-records' | 'loading-employees' | 'review' | 'settings';
 
   let step = $state<Step>('loading');
   let selectedYear = $state(0);
   let selectedMonth = $state(0);
   let records = $state<AttendanceRecord[]>([]);
   let employeeNames = $state<Record<string, string>>({});
+  // Placeholder: sovrascritti da load_settings prima che la revisione sia raggiungibile.
+  let shifts = $state<Shifts>({ in1: '', out1: '', in2: '', out2: '', round_step_min: 0 });
 
   const period = $derived(`${monthName($locale, selectedMonth)} ${selectedYear}`);
   const reviewEmployees = $derived(buildEmployees(selectedYear, selectedMonth, records, employeeNames));
 
   onMount(async () => {
-    const preferences = await invoke<{ host: string; port: number } | null>('load_preferences');
-    step = preferences ? 'confirm-month' : 'setup';
+    const settings = await invoke<SettingsData>('load_settings');
+    shifts = settings.shifts;
+    step = settings.reader.host ? 'confirm-month' : 'setup';
   });
 
+  function openSettings() {
+    clearError();
+    step = 'settings';
+  }
+
+  function closeSettings() {
+    clearError();
+    step = 'confirm-month';
+  }
+
   async function loadMonth(selection: { year: number; month: number }) {
     selectedYear = selection.year;
     selectedMonth = selection.month;
@@ -49,9 +66,17 @@
     year={selectedYear}
     month={selectedMonth}
     employees={reviewEmployees}
+    shift={shifts}
     onback={() => (step = 'confirm-month')}
     onexport={(payload) => invoke('export_timesheet', { payload })}
   />
+{:else if step === 'settings'}
+  <Settings
+    onback={closeSettings}
+    onsettingschange={(s: SettingsData) => {
+      shifts = s.shifts;
+    }}
+  />
 {:else}
   <Screen>
     {#if step === 'loading'}
@@ -59,6 +84,7 @@
     {:else if step === 'setup'}
       <Onboarding onconnected={() => (step = 'confirm-month')} />
     {:else if step === 'confirm-month'}
+      <SettingsButton ariaLabel={$_('settings.title')} onclick={openSettings} />
       <ConfirmMonth onstart={loadMonth} />
     {:else if step === 'loading-records'}
       <LoadingScreen