feat(telegram): Add Telegram group forwarding support and update button text

[abyn365]

This PR adds support for forwarding incoming emails to Telegram group/supergroup chat targets and updates the system settings dashboard to make chat ID input clearer and safer

Backend (mail-worker)

Updated telegram-service.js

Features

• Normalize and validate tgChatId values from comma-separated settings input.
• Keep chat IDs as strings to avoid numeric precision issues.
• Detect target chat type via Telegram API (getChat) before sending.
• Use:
  • web_app button for private chats
  • regular url button for group/supergroup/channel/unknown chats
• Keep existing multi-chat send behavior and continue sending even if one chat fails.
• Improve error logs with:
  • chatId
  • detected chat type
  • HTTP status
  • response body

---

Frontend (mail-vue)

Updated Telegram Settings UI (sys-setting/index.vue)

Changes

• Clarified support for:
  • user chat IDs
  • group chat IDs
  • supergroup chat IDs
• Added guidance/examples for group IDs:
  • Example: -100xxxxxxxxxx
• Kept support for comma-separated multi-ID input.
• Tightened tag validation:
  • accept signed integers only using:

    ^-?\d+$

  • automatically dedupe pasted IDs
• Updated i18n files:
  • en.js
  • zh.js
• Added new Telegram guidance/help text.

---

Compatibility / Breaking Changes

• No breaking schema or API changes.
• Existing tgChatId storage format remains:
  • comma-separated string

---

Testing

• ✅ Private chat ID still receives forwarded message with expected button behavior.
• ✅ Group/supergroup chat ID receives forwarded message successfully.
• ✅ Mixed target list (private + group) works in one forward event.
• ✅ Invalid chat IDs are ignored/rejected by UI validation.
• ✅ Existing Telegram toggle/save flow remains unchanged.