feat: add contact card spam handler for all members

[rezhajulio]

Summary

Block contact card (phone number) sharing for all non-admin members in monitored groups. Messages are deleted, users are restricted, and a notification is sent to the warning topic.

Changes

New handler: handle_contact_spam

• Detects and deletes Telegram contact card messages from non-admin members
• Restricts the user (same behavior as inline keyboard spam)
• Sends notification to warning topic (with fallback template if restrict fails)
• Registered in its own priority group (group=2) to avoid being shadowed by other handlers
• Admins and bots are exempt

Handler priority groups updated

group=-1  # topic_guard
group=0   # Commands, DM, captcha
group=1   # inline_keyboard_spam
group=2   # contact_spam (NEW)
group=3   # new_user_spam (was group=2)
group=4   # duplicate_spam (was group=3)
group=5   # message_handler (was group=4)

Files changed

• src/bot/handlers/anti_spam.py — Added has_contact() helper and handle_contact_spam() handler with restrict
• src/bot/constants.py — Added CONTACT_SPAM_NOTIFICATION and CONTACT_SPAM_NOTIFICATION_NO_RESTRICT templates
• src/bot/main.py — Registered handler, updated group numbers
• tests/test_anti_spam.py — 14 new tests (533 total, all passing)
• AGENTS.md / README.md — Updated docs, mermaid diagram with restrict step

Testing

• 533 tests, 100% pass rate
• 99.9% coverage maintained