Enhance scheduler functionality with timezone support and error handling

- Updated scheduling logic to utilize the guild's timezone for cron expressions and one-time scheduling.
- Introduced a new `getGuildTimezone` function to retrieve the timezone from guild settings.
- Enhanced error handling for scheduling inputs, providing localized error messages for invalid cron expressions and missing schedule times.
- Improved the WebUI to support a new timing mode selection (once vs. cron) and updated input fields accordingly.
- Added localization entries for new scheduling-related messages in both English and German.
- Refactored job scheduling and removal logic to ensure proper handling of scheduled jobs in the queue.

apps/webui/src/components/modules/scheduler-manager.tsx

@@ -29,10 +29,12 @@ import { Textarea } from '@/components/ui/textarea';
 import { cn } from '@/lib/utils';
 
 type ScheduleContentMode = 'text' | 'embed' | 'components_v2';
+type ScheduleTimingMode = 'once' | 'cron';
 
 const EMPTY_DRAFT = {
   channelId: '',
   contentMode: 'text' as ScheduleContentMode,
+  timingMode: 'once' as ScheduleTimingMode,
   content: '',
   embed: null as WelcomeEmbed | null,
   components: null as MessageComponentsV2 | null,
@@ -76,6 +78,19 @@ function schedulePreview(schedule: ScheduledMessageDashboard, t: (key: string) =
   return t('modulePages.scheduler.noContent');
 }
 
+function scheduleErrorMessage(code: string | undefined, t: (key: string) => string): string {
+  if (code === 'invalid_cron') {
+    return t('modulePages.scheduler.errors.invalidCron');
+  }
+  if (code === 'invalid_when') {
+    return t('modulePages.scheduler.errors.invalidWhen');
+  }
+  if (code === 'missing_schedule_time') {
+    return t('modulePages.scheduler.errors.missingScheduleTime');
+  }
+  return code?.trim() ? code : t('common.saveError');
+}
+
 interface SchedulerManagerProps {
   guildId: string;
   initialSchedules: ScheduledMessageDashboard[];
@@ -98,7 +113,10 @@ export function SchedulerManager({ guildId, initialSchedules }: SchedulerManager
       (draft.contentMode === 'embed' && (embedHasContent(embed) || embed?.color !== undefined)) ||
       (draft.contentMode === 'components_v2' && componentsV2HasContent(components));
 
-    if (!draft.channelId.trim() || !hasContent || (!draft.cron.trim() && !draft.runAt)) {
+    const cron = draft.timingMode === 'cron' ? draft.cron.trim() : '';
+    const runAt = draft.timingMode === 'once' ? draft.runAt.trim() : '';
+
+    if (!draft.channelId.trim() || !hasContent || (!cron && !runAt)) {
       toast.error(t('modulePages.scheduler.formIncomplete'));
       return;
     }
@@ -114,15 +132,16 @@ export function SchedulerManager({ guildId, initialSchedules }: SchedulerManager
           embed,
           components,
           rolePingId: draft.rolePingId.trim() || undefined,
-          cron: draft.cron.trim() || null,
-          runAt: draft.cron.trim() ? null : draft.runAt ? new Date(draft.runAt).toISOString() : null
+          // Send naive datetime-local; server interprets it in the guild timezone.
+          cron: cron || null,
+          runAt: cron ? null : runAt || null
         })
       });
       const body = (await response.json().catch(() => null)) as
         | (ScheduledMessageDashboard & { error?: string })
         | null;
       if (!response.ok || !body) {
-        toast.error(body?.error ?? t('common.saveError'));
+        toast.error(scheduleErrorMessage(body?.error, t));
         return;
       }
       setSchedules((prev) => [...prev, body]);
@@ -179,24 +198,55 @@ export function SchedulerManager({ guildId, initialSchedules }: SchedulerManager
                 placeholder={t('common.optional')}
               />
             </div>
+          </div>
+
+          <div className="space-y-2">
+            <Label>{t('modulePages.scheduler.timingMode')}</Label>
+            <div className="flex flex-wrap gap-2">
+              {(['once', 'cron'] as ScheduleTimingMode[]).map((mode) => (
+                <Button
+                  key={mode}
+                  type="button"
+                  variant={draft.timingMode === mode ? 'default' : 'outline'}
+                  size="sm"
+                  className={cn(draft.timingMode !== mode && 'text-muted-foreground')}
+                  onClick={() =>
+                    setDraft((prev) => ({
+                      ...prev,
+                      timingMode: mode,
+                      cron: mode === 'cron' ? prev.cron : '',
+                      runAt: mode === 'once' ? prev.runAt : ''
+                    }))
+                  }
+                >
+                  {t(`modulePages.scheduler.timingModes.${mode}`)}
+                </Button>
+              ))}
+            </div>
+          </div>
+
+          {draft.timingMode === 'cron' ? (
             <div className="space-y-2">
-              <Label>{t('modulePages.scheduler.cron')}</Label>
+              <Label htmlFor="scheduler-cron">{t('modulePages.scheduler.cron')}</Label>
               <Input
+                id="scheduler-cron"
                 value={draft.cron}
                 onChange={(event) => setDraft((prev) => ({ ...prev, cron: event.target.value }))}
                 placeholder="0 9 * * *"
+                autoComplete="off"
               />
             </div>
+          ) : (
             <div className="space-y-2">
-              <Label>{t('modulePages.scheduler.runAt')}</Label>
+              <Label htmlFor="scheduler-run-at">{t('modulePages.scheduler.runAt')}</Label>
               <Input
+                id="scheduler-run-at"
                 type="datetime-local"
                 value={draft.runAt}
-                disabled={Boolean(draft.cron.trim())}
                 onChange={(event) => setDraft((prev) => ({ ...prev, runAt: event.target.value }))}
               />
             </div>
-          </div>
+          )}
 
           <div className="space-y-2">
             <Label>{t('modulePages.scheduler.contentMode')}</Label>

apps/webui/src/components/ui/input.tsx

@@ -9,7 +9,7 @@ const Input = React.forwardRef<HTMLInputElement, InputProps>(({ className, type,
       type={type}
       data-slot="input"
       className={cn(
-        'flex h-9 w-full rounded-md border border-input bg-transparent px-3 py-1 text-sm shadow-sm transition-colors placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background disabled:cursor-not-allowed disabled:opacity-50',
+        'flex h-9 w-full rounded-md border border-input bg-transparent px-3 py-1 text-sm text-foreground shadow-sm transition-colors placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background disabled:cursor-not-allowed disabled:opacity-50',
         className
       )}
       ref={ref}