V2 Stage 1 Core Fixes

Base: original uploaded ZIP layout preserved.

Included in this stage:
- Duplicate ID after Done fixed by keeping the same browser session row, including when status is done.
- Live Ping: visitor page sends heartbeat to visitor_ping.php and admin dashboard shows Online/Offline.
- MX/provider badge: detects Gmail, Office/Microsoft, Yahoo, iCloud, Zoho, Proton, AOL, and Business/Other from the Email field.
- Reset Bans button: changes blocked rows back to started.
- Reset Visits button: clears visit rows and heartbeat file.
- AntiBot toggle: switches antibot_enabled setting ON/OFF and persists it.
- Support button removed.
- Original dashboard table layout is kept exactly: ID | Ping | MX | Email | Primary Email | Temporary Primary Email | Second Temporary Primary Email | Status | Actions.

Files changed:
- includes/helpers.php
- schema.sql
- visitor_ping.php
- admin/index.php
- admin/ping_status.php
- assets/style.css

Note: If your database already exists, the helper includes a small runtime migration for the new columns last_ping, client_online, and mx_provider.
