feat(ticket): record urges in thread, show urge count in admin, mail admins

- aksrt_ticket gains urge_count / last_urge_time (schema 3.1.0)
- cooldown moves from transient to an atomic conditional UPDATE
- urge inserts a system reply rendered as a centered notice (not quotable)
- admin list badge + info card row for urge count / last time
- new ticket_urge_admin mail event via aksrt_ticket_urged

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Core/DBMigratorTicket.php

@@ -31,6 +31,8 @@ trait DBMigratorTicket {
             admin_id BIGINT UNSIGNED NOT NULL DEFAULT 0,
             last_reply_admin_id BIGINT UNSIGNED NOT NULL DEFAULT 0,
             post_admin_id BIGINT UNSIGNED NOT NULL DEFAULT 0,
+            urge_count INT UNSIGNED NOT NULL DEFAULT 0,
+            last_urge_time DATETIME DEFAULT NULL,
             created_at DATETIME NOT NULL,
             updated_at DATETIME DEFAULT NULL,
             PRIMARY KEY  (id),