Add Discord bot (moderation, filters, scheduling, roles, invites, site integration)

Standalone bot/ service (its own package.json/Dockerfile) managed entirely
through a new admin-only Discord Bot panel — token stored encrypted in the
DB and pushed to the bot process in-memory, never an env var. Built in
phases, each independently verified against a live Discord guild:

- Bot skeleton: gateway connection, internal shared-secret API, self-heals
  on its own restart by pulling config from the site
- Moderation core: /ban /kick /mute /warn /warnings + mod-log channel
- Word/invite/spam filtering with leetspeak-resistant normalization and a
  staff role/channel allowlist
- Scheduled messages: recurring (cron) and one-off channel posts
- Role assignment: button role menus, auto-role on join, temp roles,
  bulk role ops
- Auto-rotating primary invite with an audit log
- Site integration: news-publish -> Discord announce webhook, manual
  /announce, read-only /wiki search

Also fixes a pre-existing bug in both DB pools (server + bot): the mariadb
driver defaulted to timezone 'local', silently mis-serializing bound Date
params by the host's local offset instead of the DB's UTC session.

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

server/.env.example

@@ -73,3 +73,12 @@ SMTP_PASS=
 CONTACT_TO=UOMysticmoon@gmail.com
 
 CLIENT_ORIGIN=http://localhost:5173
+
+# Discord bot — internal API (server <-> bot/). BOT_INTERNAL_KEY MUST be
+# byte-for-byte identical to the same variable in bot/.env.example — it is the
+# only auth on both sides' /internal/* routes, so a mismatch silently breaks
+# every server<->bot call with 401s. The Discord bot TOKEN itself is not an env
+# var — it's entered in the admin panel (Discord Bot page) and stored
+# encrypted in the DB (see the bot_config table / SECRET_ENC_KEY above).
+BOT_INTERNAL_URL=http://localhost:4100
+BOT_INTERNAL_KEY=dev-only-change-me-bot-key