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/discord/guildMemberAdd.js

@@ -0,0 +1,19 @@
+// Auto-role on join. Requires the Server Members privileged intent (already
+// enabled in the Discord Developer Portal per the Phase 1 setup notes).
+const guildConfig = require('../model/guildConfig')
+const createLogger = require('../utils/logger')
+
+const log = createLogger('autorole')
+
+async function handleGuildMemberAdd(member) {
+  try {
+    const roleId = await guildConfig.getAutoRoleId(member.guild.id)
+    if (!roleId) return
+    await member.roles.add(roleId)
+    log.info('auto-role assigned', { userId: member.id, roleId })
+  } catch (err) {
+    log.warn('auto-role assignment failed', { userId: member.id, message: err.message })
+  }
+}
+
+module.exports = { handleGuildMemberAdd }