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>

bot/src/db.js

@@ -0,0 +1,41 @@
+// DB pool for the bot's OWN tables (guild_config, mod_actions, warnings) —
+// mirrors server/src/utils/db.js. The bot never reads/writes any table it
+// doesn't own; site-owned tables (users, bot_config, etc.) are reached only
+// through the internal API, never directly. Schema for these tables lives in
+// server/db/schema.sql (same physical database, ensured by the main server on
+// boot) — there's no separate migration tool to justify a second database for
+// a single-guild v1 bot.
+const mariadb = require('mariadb')
+
+const pool = mariadb.createPool({
+  host: process.env.DB_HOST || '127.0.0.1',
+  port: Number(process.env.DB_PORT) || 3306,
+  user: process.env.DB_USER || 'root',
+  password: process.env.DB_PASSWORD || '',
+  database: process.env.DB_NAME || 'uomysticmoon',
+  connectionLimit: 5,
+  insertIdAsNumber: true,
+  bigIntAsNumber: true,
+  decimalAsNumber: true,
+  // The driver defaults to 'local' — silently serializing bound JS Date
+  // params using the HOST MACHINE's local offset instead of the DB session's
+  // timezone (discovered via temp_roles.expires_at coming back hours off in
+  // dev, CDT vs the container's UTC). 'auto' negotiates the actual session
+  // timezone so Date round-trips correctly regardless of host TZ.
+  timezone: 'auto',
+})
+
+async function query(sql, params) {
+  const conn = await pool.getConnection()
+  try {
+    return await conn.query(sql, params)
+  } finally {
+    conn.release()
+  }
+}
+
+async function close() {
+  await pool.end()
+}
+
+module.exports = { query, close }