feat: web dashboard and playground work

The NexusDashboard-parity dashboard (dDashboardServer) and everything built on it on the experimental branch:
accounts, characters, properties and moderation tools, permissions shared with in-game slash commands, economy
reports, World 3D and property 3D views with client scenery, scheduled events (features, vanity changes, live
events, announcements, restarts), vanity files and events, the CDClient browser, the message inspector with saved
captures, chat filter tools, community challenges, live ops, the AI moderator helper, and the server-side changes
they need.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

migrations/dlu/mysql/38_server_health.sql

@@ -0,0 +1,9 @@
+/* One row a minute from the dashboard: players online, running worlds, whether auth and chat were up, memory in use. */
+CREATE TABLE IF NOT EXISTS server_health (
+    time BIGINT NOT NULL PRIMARY KEY,
+    players INT UNSIGNED NOT NULL DEFAULT 0,
+    worlds INT UNSIGNED NOT NULL DEFAULT 0,
+    auth_online TINYINT NOT NULL DEFAULT 0,
+    chat_online TINYINT NOT NULL DEFAULT 0,
+    memory_kb BIGINT UNSIGNED NOT NULL DEFAULT 0
+);