Fix bot container inheriting site PORT/LOG_FILE from shared .env

The app and bot services share env_file: .env, so the site's PORT=3000
leaked into the bot container. The bot code is `PORT || 4100`, so it
bound 3000 instead of 4100 — and the server's BOT_INTERNAL_URL
(http://bot:4100) then couldn't reach it, surfacing as "failed to fetch"
on the admin Discord Bot page even though the bot was otherwise healthy
and connected to Discord.

Pin PORT: 4100 on the bot service so it binds where the server expects.
Also override LOG_FILE: bot.log so the bot doesn't inherit the site's
LOG_FILE and write into app.log, keeping the two logs distinct.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019rao86n5cXpwAyjdBFEshV

docker-compose.yml

@@ -51,6 +51,14 @@ services:
     env_file: .env
     environment:
       DB_HOST: db
+      # Pin the bot's own listen port. Both services share env_file: .env, so
+      # without this the site's PORT=3000 leaks in and the bot binds 3000 instead
+      # of 4100 — then the server's BOT_INTERNAL_URL (http://bot:4100) can't reach
+      # it ("failed to fetch" in the admin panel). Must match that URL's port.
+      PORT: 4100
+      # Likewise override the log filename so the bot doesn't inherit the site's
+      # LOG_FILE and write into app.log — keep the bot's log distinct.
+      LOG_FILE: bot.log
       # Internal config fetch goes to the app's UNPUBLISHED internal port (3001),
       # not the public 3000. Keep the port in sync with the app's INTERNAL_PORT.
       SITE_INTERNAL_URL: http://app:3001/internal/bot-config