Make scheduling and dates timezone-safe

apps/mobile/app/(app)/invoices/send/[id].tsx

@@ -20,7 +20,9 @@ import { DateTimeField } from "@/components/ui/DateTimeField";
 import {
   formatZonedDateTime,
   getDefaultScheduledSendAt,
-  getLocalTimeZone,
+  DEFAULT_TIME_ZONE,
+  toLocalDateTimeInputValue,
+  zonedDateTimeToInstant,
 } from "@beenvoice/domain/time-zone";
 import { fonts, spacing } from "@/constants/theme";
 import { useAppTheme } from "@/contexts/ThemeContext";
@@ -42,7 +44,8 @@ export default function InvoiceSendScreen() {
   const [scheduledAt, setScheduledAt] = useState(() =>
     getDefaultScheduledSendAt(),
   );
-  const timeZone = useMemo(() => getLocalTimeZone(), []);
+  const profileQuery = api.settings.getProfile.useQuery();
+  const timeZone = profileQuery.data?.timeZone ?? DEFAULT_TIME_ZONE;
 
   const invoiceQuery = api.invoices.getById.useQuery(
     { id: id ?? "" },
@@ -139,7 +142,21 @@ export default function InvoiceSendScreen() {
 
   function handleSchedule() {
     if (!clientEmail || invoice.items.length === 0) return;
-    if (scheduledAt.getTime() < Date.now() + 60_000) {
+    let instant: Date;
+    try {
+      instant = zonedDateTimeToInstant(
+        toLocalDateTimeInputValue(scheduledAt),
+        timeZone,
+        "earlier",
+      );
+    } catch (error) {
+      Alert.alert(
+        "Choose another time",
+        error instanceof Error ? error.message : "Invalid local time",
+      );
+      return;
+    }
+    if (instant.getTime() < Date.now() + 60_000) {
       Alert.alert(
         "Choose a future time",
         "The scheduled time must be at least one minute from now.",
@@ -148,7 +165,7 @@ export default function InvoiceSendScreen() {
     }
     scheduleInvoice.mutate({
       invoiceId: invoice.id,
-      scheduledAt,
+      scheduledAt: instant,
       timeZone,
       customMessage: customMessage.trim() || undefined,
     });