Implement leave announcement for banned members and enhance moderation notifications

- Added a `leaveAnnounceBan` field to the `WelcomeConfig` model, allowing for optional announcements in the leave channel when a member is banned.
- Updated the leave handling logic to check for bans and send a notice in the leave channel if the `leaveAnnounceBan` toggle is enabled.
- Enhanced moderation actions (kick and ban) to notify the affected user via DM with the reason for the action.
- Introduced a new `notifyModerationTargetDm` function to streamline DM notifications for moderation actions.
- Updated the WebUI to include a toggle for the `leaveAnnounceBan` feature, improving user configurability.
- Improved localization for new messages related to moderation notifications and leave announcements in both English and German.
- Documented changes in phase tracking to reflect the new leave announcement feature and moderation notification enhancements.

apps/webui/src/components/modules/welcome-form.tsx

@@ -252,6 +252,22 @@ export function WelcomeForm({ guildId, initialValue, previewVars }: WelcomeFormP
                 />
               </div>
               </FieldAnchor>
+              <FieldAnchor id="field-leave-announce-ban">
+              <div className="flex items-center justify-between gap-4 rounded-md border border-border p-4">
+                <div className="space-y-1">
+                  <Label>{t('modulePages.welcome.leaveAnnounceBanLabel')}</Label>
+                  <p className="text-sm text-muted-foreground">
+                    {t('modulePages.welcome.leaveAnnounceBanHint')}
+                  </p>
+                </div>
+                <Switch
+                  checked={value.leaveAnnounceBan}
+                  onCheckedChange={(checked) =>
+                    setValue((prev) => ({ ...prev, leaveAnnounceBan: checked }))
+                  }
+                />
+              </div>
+              </FieldAnchor>
               <FieldAnchor id="field-leave-channel">
               <div className="space-y-2">
                 <Label>{t('modulePages.welcome.leaveChannelId')}</Label>