Revert ReminderForm to single datetime-local input

Matches EventForm pattern used across UMBRA. Remind At and Recurrence
now sit side-by-side in a 2-column grid. Empty optional fields send
null instead of empty string.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/reminders/ReminderForm.tsx

@@ -22,53 +22,28 @@ interface ReminderFormProps {
   onClose: () => void;
 }
 
-function parseRemindAt(remindAt?: string) {
-  if (!remindAt) return { date: '', hour: '12', minute: '00', period: 'PM' as const };
-  const d = new Date(remindAt);
-  const date = `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`;
-  let hours = d.getHours();
-  const period = hours >= 12 ? 'PM' as const : 'AM' as const;
-  hours = hours % 12 || 12;
-  return {
-    date,
-    hour: String(hours),
-    minute: String(d.getMinutes()).padStart(2, '0'),
-    period,
-  };
-}
-
-function buildRemindAt(date: string, hour: string, minute: string, period: 'AM' | 'PM'): string {
-  if (!date) return '';
-  let h = parseInt(hour, 10);
-  if (period === 'AM' && h === 12) h = 0;
-  else if (period === 'PM' && h !== 12) h += 12;
-  return `${date}T${String(h).padStart(2, '0')}:${minute}`;
-}
-
 export default function ReminderForm({ reminder, onClose }: ReminderFormProps) {
   const queryClient = useQueryClient();
-  const parsed = parseRemindAt(reminder?.remind_at);
-  const [title, setTitle] = useState(reminder?.title || '');
-  const [description, setDescription] = useState(reminder?.description || '');
-  const [date, setDate] = useState(parsed.date);
-  const [hour, setHour] = useState(parsed.hour);
-  const [minute, setMinute] = useState(parsed.minute);
-  const [period, setPeriod] = useState<'AM' | 'PM'>(parsed.period);
-  const [recurrenceRule, setRecurrenceRule] = useState(reminder?.recurrence_rule || '');
+  const [formData, setFormData] = useState({
+    title: reminder?.title || '',
+    description: reminder?.description || '',
+    remind_at: reminder?.remind_at ? reminder.remind_at.slice(0, 16) : '',
+    recurrence_rule: reminder?.recurrence_rule || '',
+  });
 
   const mutation = useMutation({
-    mutationFn: async () => {
-      const data = {
-        title,
-        description: description || null,
-        remind_at: buildRemindAt(date, hour, minute, period) || null,
-        recurrence_rule: recurrenceRule || null,
+    mutationFn: async (data: typeof formData) => {
+      const payload = {
+        ...data,
+        description: data.description || null,
+        remind_at: data.remind_at || null,
+        recurrence_rule: data.recurrence_rule || null,
       };
       if (reminder) {
-        const response = await api.put(`/reminders/${reminder.id}`, data);
+        const response = await api.put(`/reminders/${reminder.id}`, payload);
         return response.data;
       } else {
-        const response = await api.post('/reminders', data);
+        const response = await api.post('/reminders', payload);
         return response.data;
       }
     },
@@ -86,7 +61,7 @@ export default function ReminderForm({ reminder, onClose }: ReminderFormProps) {
 
   const handleSubmit = (e: FormEvent) => {
     e.preventDefault();
-    mutation.mutate();
+    mutation.mutate(formData);
   };
 
   return (
@@ -102,8 +77,8 @@ export default function ReminderForm({ reminder, onClose }: ReminderFormProps) {
               <Label htmlFor="title" required>Title</Label>
               <Input
                 id="title"
-                value={title}
-                onChange={(e) => setTitle(e.target.value)}
+                value={formData.title}
+                onChange={(e) => setFormData({ ...formData, title: e.target.value })}
                 required
               />
             </div>
@@ -112,67 +87,37 @@ export default function ReminderForm({ reminder, onClose }: ReminderFormProps) {
               <Label htmlFor="description">Description</Label>
               <Textarea
                 id="description"
-                value={description}
-                onChange={(e) => setDescription(e.target.value)}
+                value={formData.description}
+                onChange={(e) => setFormData({ ...formData, description: e.target.value })}
                 className="min-h-[80px] flex-1"
               />
             </div>
 
-            <div className="space-y-2">
-              <Label htmlFor="remind_date">Remind At</Label>
-              <div className="flex items-center gap-2">
+            <div className="grid grid-cols-2 gap-4">
+              <div className="space-y-2">
+                <Label htmlFor="remind_at">Remind At</Label>
                 <Input
-                  id="remind_date"
-                  type="date"
-                  value={date}
-                  onChange={(e) => setDate(e.target.value)}
-                  className="flex-1"
+                  id="remind_at"
+                  type="datetime-local"
+                  value={formData.remind_at}
+                  onChange={(e) => setFormData({ ...formData, remind_at: e.target.value })}
                 />
+              </div>
+
+              <div className="space-y-2">
+                <Label htmlFor="recurrence">Recurrence</Label>
                 <Select
-                  value={hour}
-                  onChange={(e) => setHour(e.target.value)}
-                  className="w-[4.5rem]"
+                  id="recurrence"
+                  value={formData.recurrence_rule}
+                  onChange={(e) => setFormData({ ...formData, recurrence_rule: e.target.value })}
                 >
-                  {Array.from({ length: 12 }, (_, i) => i + 1).map((h) => (
-                    <option key={h} value={String(h)}>{h}</option>
-                  ))}
-                </Select>
-                <span className="text-muted-foreground">:</span>
-                <Select
-                  value={minute}
-                  onChange={(e) => setMinute(e.target.value)}
-                  className="w-[4.5rem]"
-                >
-                  {Array.from({ length: 12 }, (_, i) => i * 5).map((m) => (
-                    <option key={m} value={String(m).padStart(2, '0')}>
-                      {String(m).padStart(2, '0')}
-                    </option>
-                  ))}
-                </Select>
-                <Select
-                  value={period}
-                  onChange={(e) => setPeriod(e.target.value as 'AM' | 'PM')}
-                  className="w-[4.5rem]"
-                >
-                  <option value="AM">AM</option>
-                  <option value="PM">PM</option>
+                  <option value="">None</option>
+                  <option value="daily">Daily</option>
+                  <option value="weekly">Weekly</option>
+                  <option value="monthly">Monthly</option>
                 </Select>
               </div>
             </div>
-
-            <div className="space-y-2">
-              <Label htmlFor="recurrence">Recurrence</Label>
-              <Select
-                id="recurrence"
-                value={recurrenceRule}
-                onChange={(e) => setRecurrenceRule(e.target.value)}
-              >
-                <option value="">None</option>
-                <option value="daily">Daily</option>
-                <option value="weekly">Weekly</option>
-                <option value="monthly">Monthly</option>
-              </Select>
-            </div>
           </div>
 
           <SheetFooter>