Implement PlaceholderHelp component across various forms for enhanced user guidance

- Integrated PlaceholderHelp component into multiple forms including WelcomeForm, TagsManager, and StatsForm to provide contextual hints for available placeholders.
- Updated DiscordEmbedBuilder to support placeholder presets, improving user experience when creating embeds.
- Enhanced localization files to include new placeholder descriptions, ensuring clarity in both English and German.
- Refactored related components to maintain consistency in placeholder handling across the application.

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

@@ -9,6 +9,7 @@ import { DiscordChannelSelect } from '@/components/ui/discord-channel-select';
 import { DiscordRoleSelect } from '@/components/ui/discord-role-select';
 import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';
+import { PlaceholderHelp } from '@/components/ui/placeholder-help';
 import { Switch } from '@/components/ui/switch';
 import { Textarea } from '@/components/ui/textarea';
 import type { SettingsSaveResult } from '@/components/settings/settings-form';
@@ -87,6 +88,7 @@ export function BirthdaysForm({ guildId, initialValue }: BirthdaysFormProps) {
             <div className="space-y-2">
               <Label>{t('modulePages.birthdays.message')}</Label>
               <Textarea value={value.message ?? ''} onChange={(event) => setValue((prev) => ({ ...prev, message: event.target.value || null }))} placeholder={t('modulePages.birthdays.messagePlaceholder')} />
+              <PlaceholderHelp preset="birthdays" />
             </div>
             </FieldAnchor>
           </CardContent>