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/commands/wiki.command.js

@@ -0,0 +1,40 @@
+const { ApplicationCommandOptionType } = require('discord.js')
+
+const siteApiClient = require('../../site/siteApiClient')
+
+// Public command — no default_member_permissions restriction. Read-only:
+// searches wiki titles/content and links to the best match. Never posts to or
+// edits the wiki. Category-scoped search (spec's optional "/wiki spells
+// fireball") is deferred — the site's public search endpoint currently
+// ignores category filters whenever a text query is given.
+function siteOrigin() {
+  const base = process.env.SITE_PUBLIC_URL || 'http://localhost:3000/api/v1/public'
+  return new URL(base).origin
+}
+
+module.exports = {
+  data: {
+    name: 'wiki',
+    description: 'Search the wiki.',
+    options: [{ name: 'query', description: 'What to search for', type: ApplicationCommandOptionType.String, required: true }],
+  },
+  async execute(interaction) {
+    const query = interaction.options.getString('query', true)
+    await interaction.deferReply()
+
+    const result = await siteApiClient.searchWiki(query)
+    if (result.maintenance) {
+      await interaction.editReply({ content: `The wiki is unavailable right now: ${result.message || 'maintenance mode'}` })
+      return
+    }
+    if (!result.ok || !result.data || result.data.length === 0) {
+      await interaction.editReply({ content: `No wiki results for "${query}".` })
+      return
+    }
+
+    const best = result.data[0]
+    const url = `${siteOrigin()}/wiki/${best.slug}`
+    const content = best.excerpt ? `**${best.title}**\n${best.excerpt}\n${url}` : `**${best.title}**\n${url}`
+    await interaction.editReply({ content })
+  },
+}