fix(teams): pipe TEAMS_PORT through docker-compose properly

Was hardcoded to 3978; use ${TEAMS_PORT:-3978} so a custom port
set in .env is actually passed into the container.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -40,7 +40,7 @@ services:
       # - TEAMS_CLIENT_SECRET=${TEAMS_CLIENT_SECRET}
       # - TEAMS_TENANT_ID=${TEAMS_TENANT_ID}
       # - TEAMS_ALLOWED_USERS=${TEAMS_ALLOWED_USERS}
-      # - TEAMS_PORT=3978
+      # - TEAMS_PORT=${TEAMS_PORT:-3978}
     command: ["gateway", "run"]
 
   dashboard: