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/scheduler/scheduler.js

@@ -0,0 +1,83 @@
+// Recurring + one-off scheduled channel messages. Recurring rows are each
+// registered as their own node-cron task; one-off rows are picked up by a
+// once-a-minute sweep that checks for anything due and marks it sent so it
+// never reposts. Needs a live discord.js Client to actually send — wired up
+// by discordManager.js (start() once the client is ready, stop() alongside
+// client teardown).
+const cron = require('node-cron')
+
+const scheduledMessages = require('../model/scheduledMessages')
+const createLogger = require('../utils/logger')
+
+const log = createLogger('scheduler')
+
+let discordClient = null
+const recurringTasks = new Map() // id -> node-cron ScheduledTask
+let sweepTask = null
+
+async function sendToChannel(channelId, content) {
+  try {
+    const channel = await discordClient.channels.fetch(channelId)
+    if (!channel || !channel.isTextBased()) {
+      log.warn('scheduled message skipped — channel missing or not text-based', { channelId })
+      return
+    }
+    await channel.send({ content })
+    log.info('sent scheduled message', { channelId })
+  } catch (err) {
+    log.warn('failed to send scheduled message', { channelId, message: err.message })
+  }
+}
+
+async function loadRecurring() {
+  for (const task of recurringTasks.values()) task.stop()
+  recurringTasks.clear()
+
+  const rows = await scheduledMessages.listEnabledRecurring()
+  for (const row of rows) {
+    if (!cron.validate(row.cron_expression)) {
+      log.warn('skipping scheduled message with invalid cron expression', { id: row.id, cron: row.cron_expression })
+      continue
+    }
+    const task = cron.schedule(row.cron_expression, () => sendToChannel(row.channel_id, row.content))
+    recurringTasks.set(row.id, task)
+  }
+  log.info('loaded recurring scheduled messages', { count: recurringTasks.size })
+}
+
+async function sweepDueOneOff() {
+  try {
+    const due = await scheduledMessages.listDueOneOff()
+    for (const row of due) {
+      await sendToChannel(row.channel_id, row.content)
+      await scheduledMessages.markSent(row.id)
+    }
+  } catch (err) {
+    log.error('one-off sweep failed', { message: err.message })
+  }
+}
+
+async function start(client) {
+  discordClient = client
+  await loadRecurring()
+  sweepTask = cron.schedule('* * * * *', sweepDueOneOff)
+  log.info('scheduler started')
+}
+
+// Called by /schedule after any add/remove so changes apply without a restart.
+async function refresh() {
+  if (!discordClient) return
+  await loadRecurring()
+}
+
+function stop() {
+  for (const task of recurringTasks.values()) task.stop()
+  recurringTasks.clear()
+  if (sweepTask) {
+    sweepTask.stop()
+    sweepTask = null
+  }
+  discordClient = null
+}
+
+module.exports = { start, stop, refresh }