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/66_slash_command_targets.sql

@@ -0,0 +1,8 @@
+/* slash_commands.target_rule: who a command may be used on, by the dashboard's self and rank rules (SlashCommandLevels::eTargetRule):
+   '' (acts on nobody else), 'tools', 'items' or 'moderation' (on yourself with self_tools, self_items or self_moderation),
+   or 'others' (checked on other players only). Written by the world servers like the rest of the row.
+   slash_commands.follows_permission: 1 when the command uses its dashboard_permission's level (written by servers that know
+   this). Rows from before are 0, which is how a world tells that a server is upgrading and keeps the level each paired command
+   had then as an override (command_level_<name>, updated_by '[upgrade]'). */
+ALTER TABLE slash_commands ADD COLUMN target_rule VARCHAR(16) NOT NULL DEFAULT '';
+ALTER TABLE slash_commands ADD COLUMN follows_permission TINYINT NOT NULL DEFAULT 0;