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/bot/src/modules/scheduler/service.ts

@@ -5,7 +5,7 @@ import {
   type MessageCreateOptions,
   type TextChannel
 } from 'discord.js';
-import { WelcomeEmbedSchema, t, tf } from '@nexumi/shared';
+import { WelcomeEmbedSchema, expandBracketChannelMentions, t, tf } from '@nexumi/shared';
 import type { ScheduledMessage } from '@prisma/client';
 import { ensureGuild } from '../../guild.js';
 import { logger } from '../../logger.js';
@@ -99,15 +99,15 @@ export function buildAnnouncementPayload(schedule: {
   if (embedData) {
     const embed = new EmbedBuilder().setColor(embedData.color ?? 0x6366f1);
     if (embedData.title) {
-      embed.setTitle(embedData.title);
+      embed.setTitle(expandBracketChannelMentions(embedData.title));
     }
     if (embedData.description) {
-      embed.setDescription(embedData.description);
+      embed.setDescription(expandBracketChannelMentions(embedData.description));
     }
     embeds.push(embed);
   }
 
-  const baseContent = schedule.content?.trim() ?? '';
+  const baseContent = expandBracketChannelMentions(schedule.content?.trim() ?? '');
   const roleMention = schedule.rolePingId ? `<@&${schedule.rolePingId}>` : '';
   const content = [roleMention, baseContent].filter(Boolean).join(' ').trim();