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/news.command.js

@@ -0,0 +1,31 @@
+const { PermissionFlagsBits, ApplicationCommandOptionType, ChannelType } = require('discord.js')
+
+const guildConfig = require('../../model/guildConfig')
+
+module.exports = {
+  data: {
+    name: 'news',
+    description: 'View or set the channel news posts are announced to.',
+    default_member_permissions: PermissionFlagsBits.ManageGuild.toString(),
+    options: [
+      {
+        name: 'channel',
+        description: 'Channel for news announcements. Omit to view the current setting.',
+        type: ApplicationCommandOptionType.Channel,
+        channel_types: [ChannelType.GuildText],
+        required: false,
+      },
+    ],
+  },
+  async execute(interaction) {
+    const channel = interaction.options.getChannel('channel')
+    if (!channel) {
+      const currentId = await guildConfig.getNewsChannelId(interaction.guildId)
+      const content = currentId ? `News channel is set to <#${currentId}>.` : 'No news channel is set yet.'
+      await interaction.reply({ content, ephemeral: true })
+      return
+    }
+    await guildConfig.setNewsChannelId(interaction.guildId, channel.id)
+    await interaction.reply({ content: `News channel set to ${channel}.`, ephemeral: true })
+  },
+}