fix: use correct relative path for RTC config mount

Changed from ./drop/rtc_config.json to ./rtc_config.json since the
compose file is already in the drop/ directory. The previous path
caused Docker to create an empty directory instead of mounting the file.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

drop/compose.yaml

@@ -4,7 +4,7 @@ services:
     container_name: ${DROP_COMPOSE_PROJECT_NAME}_app
     restart: unless-stopped
     volumes:
-      - ./drop/rtc_config.json:/rtc_config.json:ro
+      - ./rtc_config.json:/rtc_config.json:ro
     environment:
       PUID: 1000
       PGID: 1000