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>

.env.example

@@ -12,7 +12,8 @@ LOG_TO_FILE=true        # set false for console-only
 LOG_DIR=/app/logs       # log directory inside the container (bind-mounted to ./logs)
 LOG_FILE=app.log
 
-# Database (the values here are shared by the `db` and `app` containers)
+# Database (the values here are shared by the `db`, `app`, and `bot` containers —
+# the bot only ever touches its own tables: guild_config, mod_actions, warnings)
 DB_HOST=db
 DB_PORT=3306
 DB_NAME=uomysticmoon
@@ -58,3 +59,12 @@ CONTACT_TO=UOMysticmoon@gmail.com
 
 # CORS — only needed for local dev when the Vite dev server is a different origin.
 CLIENT_ORIGIN=http://localhost:5173
+
+# Discord bot — internal API (server <-> bot/, see docker-compose.yml's `bot`
+# service). 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 bot_config table).
+BOT_INTERNAL_URL=http://bot:4100
+BOT_INTERNAL_KEY=change-me-to-a-long-random-string