refactor: switch to dedicated group, remove @mention requirement, add pinned message service

- Change ALLOWED_GROUP to Dienst opvragen EdGPT-EBS (120363407613652082@g.us)
- Remove isBotMentioned check (no @mention needed)
- Match only exact 4-digit messages (regex /^\s*(\d{4})\s*$/)
- Add pinnedMessageService.js: auto-repins welcome message when expired
- Move incrementDaily() to count all 4-digit messages, not just successful ones
- Update daily summary with emoji
- Update docs and .env.example

src/index.js

@@ -37,7 +37,7 @@ cron.schedule('0 10 * * *', () => {
   resetDay()
   const total = getYesterdayTotal()
 
-  sendTextMessage(adminNumber, `Aantal dienstaanvragen gisteren: ${total}`)
+  sendTextMessage(adminNumber, `📊 Aantal dienstaanvragen gisteren: ${total}`)
     .then(() => console.log(`Daily summary sent: ${total} requests`))
     .catch(err => console.error('Failed to send daily summary:', err.message))
 })