discord-bridge: Matrix avatars on Discord, catch up missed messages

Set bridge.public_address so relayed messages carry the sender's avatar
(served through a new NPM location for /mautrix-discord/avatar/), listen
on 0.0.0.0 so NPM can reach it, and backfill all Discord messages missed
while the bridge was down.

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

README.md

@@ -290,7 +290,7 @@ The token in `draupnir/production.yaml` in this repo is **intentionally redacted
 | 9002 | Hookshot bridge (appservice) | 127.0.0.1 |
 | 9003 | Hookshot webhooks | 0.0.0.0 |
 | 9004 | Hookshot metrics | 0.0.0.0 |
-| 29334 | mautrix-discord (appservice) | 127.0.0.1 |
+| 29334 | mautrix-discord (appservice + avatar proxy for NPM) | 0.0.0.0 |
 | 9100 | node_exporter | 0.0.0.0 |
 | 9101 | matrix-admin exporter | 0.0.0.0 |
 | 9500 | webhook (auto-deploy) | 0.0.0.0 |
@@ -427,8 +427,15 @@ can't overwrite the room's name and icon with the Discord channel's.
 **Rotating the bot token:** reset it in the Developer Portal, then DM the bridge bot `logout` and
 `login-token bot <new token>`.
 
-**Not set up yet:** `bridge.public_address`, so Matrix users' avatars aren't shown on their relayed
-Discord messages (names are). It needs a public NPM route to `/mautrix-discord/avatar/`.
+**Matrix avatars on Discord:** relayed messages carry the sender's avatar as a signed URL under
+`bridge.public_address` (`https://matrix.lotusguild.org`), which Discord fetches. NPM proxies
+`/mautrix-discord/avatar/` → `http://10.10.10.29:29334` (hand-added location in
+`/data/nginx/proxy_host/49.conf` on LXC 139, like `/sfu/get` — **re-add it after any NPM UI save of
+proxy host 49**). The bridge listens on `0.0.0.0:29334` for this; the appservice API on that port
+still requires the `hs_token`, and only the avatar path is proxied publicly.
+
+**Catch-up after downtime:** `backfill.forward_limits.missed.channel: -1`, so Discord messages sent
+while the bridge or Synapse was down are bridged when it starts again.
 
 ---
 

discord-bridge/config.yaml

@@ -31,7 +31,7 @@ appservice:
     address: http://127.0.0.1:29334
 
     # The hostname and port where this appservice should listen.
-    hostname: 127.0.0.1
+    hostname: 0.0.0.0
     port: 29334
 
     # Database config.
@@ -114,7 +114,7 @@ bridge:
     # Publicly accessible base URL that Discord can use to reach the bridge, used for avatars in relay mode.
     # If not set, avatars will not be bridged. Only the /mautrix-discord/avatar/{server}/{id}/{hash} endpoint is used on this address.
     # This should not have a trailing slash, the endpoint above will be appended to the provided address.
-    public_address: null
+    public_address: https://matrix.lotusguild.org
     # A random key used to sign the avatar URLs. The bridge will only accept requests with a valid signature.
     avatar_proxy_key: generate
 
@@ -257,7 +257,7 @@ bridge:
             # With limits, all messages up to the limit are fetched first and backfilled afterwards.
             missed:
                 dm: 0
-                channel: 0
+                channel: -1
                 thread: 0
         # Maximum members in a guild to enable backfilling. Set to -1 to disable limit.
         # This can be used as a rough heuristic to disable backfilling in channels that are too active.