discord-bridge: bot profile, down alert, login-owner account

Add the Discord-logo avatar and a script that uploads it as the bridge
bot and sets the display name to "Discord Bridge". Document the new
"Discord Bridge Down" Grafana alert, and why the bot login belongs on a
dedicated non-chatting account: whoever holds it sends to Discord as the
bot instead of through the relay webhook.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

README.md

@@ -424,6 +424,15 @@ Skip `guilds bridge`: it sets the guild to create a Matrix room for every channe
 old room). The relay webhook stays with the channel. Keep `@discordbot` at the default power level so it
 can't overwrite the room's name and icon with the Discord channel's.
 
+**Bot profile:** `@discordbot` shows as "Discord Bridge" with the Discord logo
+(`discord-bridge/bot-avatar.png`). To reapply it: `pct exec 151 -- bash /opt/matrix-config/discord-bridge/set-bot-profile.sh`.
+
+**Who the Discord bot login belongs to:** whichever Matrix account ran `login-token bot` sends its own
+messages to Discord *as the bot* ("matrix-bridge APP"), not through the relay webhook. So it lives on a
+dedicated account, `@discord-relay:matrix.lotusguild.org`, which never chats. Everyone else, admins
+included, stays logged out of the bridge and is relayed under their own name and avatar. Logging the
+bot in on one account automatically logs out any other account that had it.
+
 **Rotating the bot token:** reset it in the Developer Portal, then DM the bridge bot `logout` and
 `login-token bot <new token>`.
 
@@ -1006,6 +1015,7 @@ Checklist in this file.
 | PostgreSQL Down | `pg_up` < 1 for 2m | critical |
 | LiveKit Down | `up{job="livekit"}` < 1 for 2m | critical |
 | Hookshot Down | `up{job="hookshot"}` < 1 for 2m | critical |
+| Discord Bridge Down | `node_systemd_unit_state{name="mautrix-discord.service",state="active"}` < 1 (or no data) for 3m | critical |
 | Draupnir Down | `up{job="draupnir-node"}` < 0.5 for 2m | critical |
 | PG Connection Saturation | connections > 80% of max for 5m | warning |
 | Federation Queue Backing Up | pending PDUs > 100 for 10m | warning |

discord-bridge/config.yaml

@@ -61,7 +61,7 @@ appservice:
         username: discordbot
         # Display name and avatar for bot. Set to "remove" to remove display name/avatar, leave empty
         # to leave display name/avatar as-is.
-        displayname: Discord bridge bot
+        displayname: Discord Bridge
         avatar: mxc://maunium.net/nIdEykemnwdisvHbpxflpDlC
 
     # Whether or not to receive ephemeral events via appservice transactions.

discord-bridge/set-bot-profile.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+# Gives @discordbot the Discord logo and the display name "Discord Bridge".
+# Run inside LXC 151 (from the Proxmox node):
+#   pct exec 151 -- bash /opt/matrix-config/discord-bridge/set-bot-profile.sh
+# Uploads bot-avatar.png as the bridge bot, points config.yaml at it and
+# restarts the bridge, which applies the profile on startup. Safe to re-run.
+set -euo pipefail
+
+DIR=/opt/mautrix-discord
+CFG="$DIR/config.yaml"
+AVATAR=/opt/matrix-config/discord-bridge/bot-avatar.png
+BOT="@discordbot:matrix.lotusguild.org"
+
+AS_TOKEN=$(awk '/^as_token:/ {gsub(/"/, "", $2); print $2; exit}' "$DIR/registration.yaml")
+[ -n "$AS_TOKEN" ] || { echo "no as_token in $DIR/registration.yaml" >&2; exit 1; }
+
+MXC=$(curl -fsS -X POST \
+    -H "Authorization: Bearer $AS_TOKEN" \
+    -H "Content-Type: image/png" \
+    --data-binary "@$AVATAR" \
+    "http://127.0.0.1:8008/_matrix/media/v3/upload?filename=discord.png&user_id=${BOT/@/%40}" |
+    python3 -c 'import json, sys; print(json.load(sys.stdin)["content_uri"])')
+echo "uploaded $MXC"
+
+# Only the bot block's two lines; the 8-space indent is unique to appservice.bot.
+sed -i -E \
+    -e 's|^(        displayname: ).*$|\1Discord Bridge|' \
+    -e "s|^(        avatar: )mxc://.*$|\1$MXC|" \
+    "$CFG"
+grep -A7 '^    bot:' "$CFG"
+
+systemctl restart mautrix-discord
+sleep 3
+systemctl is-active mautrix-discord